AIO Am I overreacting by thinking that one of my mutual friends is competing for my boyfriend's attention, who is also her friend?

Apologies in advance, I think this will be very long.

My boyfriend (25M) and I have been together for a little over a year, and the truth is we haven't had any major arguments. The few we've had have been resolved as calmly and patiently as possible because my boyfriend likes to resolve things in the moment, calmly, and by speaking directly and calmly.

To clarify, neither of us is jealous or possessive of the other, so we can each go out with our friends individually and there's no problem. (Here's an important point to emphasize: I have been in a toxic relationship, where there was manipulation and possessiveness from my partner, and it was horrible. I absolutely don't plan to repeat that experience. That's why I made this point clear to my boyfriend from the beginning, and there were no objections. It's also why I think things through very carefully before turning them into an argument or a problem in the relationship. I try to make sure that what I consider a "problem" is truly a problem and not just me and my raging hormones making a mountain out of a molehill. I know myself, and I know that's how I am, so I think a lot before expressing it and not burdening the relationship with nonsense. My boyfriend is perfectly aware of this and asks me to let him know in any way I can.)

So the problem arises because we both have a mutual friend. She met me first, then she met him, and then she introduced us, and we started dating—in that order I just mentioned. So she's been present since the beginning of this relationship. This friend likes a chaotic life; she doesn't know how to be alone, without a relationship. She barely ended her relationship due to infidelity and started another one with someone long-distance while also cheating on him with other people. My boyfriend and our mutual friends know her, and the truth is, we don't care what she does as long as it doesn't directly affect us. She hadn't caused any problems until now.

Today we had an event where my boyfriend, me, and her were present. She was holding hands with a friend she'd been using as a "fake/game" boyfriend for a few months. At first, everything was fine. My boyfriend was busy with his own things, I with mine, and she and that friend I mentioned earlier were dragging him around (helping her with things that weren't really related to the event, but rather things like moving her belongings or just showing off and chatting). When he left, she started doing the same thing with my boyfriend. Sometimes he played along and helped her, then after a while he ignored her because he was busy, and sometimes she'd come over to give me a kiss or a hug and then leave. Up to that point, everything was fine.

In one of those moments when she wanted me to follow her around and chat, she appeared with my boyfriend, arm in arm, and I joined them. I followed them, but honestly, I couldn't have a conversation with her because she would abruptly change the subject, sometimes cutting me off mid-sentence, and other times giving me obvious answers that made me feel stupid for asking the question. Besides, I couldn't talk to my boyfriend either because she would monopolize his attention, either by speaking louder than me or by calling him repeatedly while he looked at me to listen. She would insist until he finally turned around to pay attention so she could say whatever she had to say.

This type of behavior has happened several times before, mainly when it's just the three of us. When there's a fourth person, this problem doesn't usually occur, although it can happen. The difference is that today she crossed the line when she started talking much louder than me, almost shouting, with slight tugs on his arm, and insisting so much that she interrupted my conversation with my boyfriend to get his attention. Because of this insistence, my boyfriend turned away, and she just told him what items she was going to buy and asked for his opinion. Even the guy who was helping us made a reference to her being his girlfriend, saying something like, "His girlfriend is very demanding," or something similar, since I don't remember exactly. I just let go of his arm (she still had it) and stood next to them, but they continued their conversation. They didn't even pay attention to what the guy had said. I moved further away, pretending to be on my phone, and then I simply went back to the same place where I had been busy before, although this time I was doing nothing but playing on my phone. An hour passed before I saw my boyfriend again. He gave me a kiss like before and showed me some things he had bought, and that was it. After a couple more hours, my friend had already left, and my My boyfriend and I left together, and he asked me if I was tired and why I seemed so "down." I told him I was definitely tired and also annoyed, but I wasn't sure if it was something I really should be upset about or if it was just because I'm on my period and everything makes me angry/cry for no apparent reason. Also, I should clarify that I'm very resentful. I'm not jealous or possessive, but I do get very resentful if I feel like I'm not getting the same attention I give, and he knows this.

I explained everything I just told you, and he said it was completely valid for me to be upset because our friend is always looking for attention, and since he didn't want to ignore her to avoid making her feel bad, he didn't realize he was neglecting me in the process. He promised that from now on, all his attention would be focused on me. And this is where I told him I felt like I was overreacting, making a big deal out of nothing, and being possessive. He said I wasn't, and besides, he doesn't mind a little bit of possessiveness, and that he knows I'll always give him the freedom to be and do whatever he wants.

I can't talk about this with my other friends in the group because I'm afraid they'll label me as jealous and possessive, and I swear that's the last thing I want to do.

And in case you're wondering why she was holding our friend's hand or my boyfriend's arm, it's a habit she says she has. She says it gives her anxiety, so she holds my arm, or my boyfriend's, or another friend's arm.

While writing all this, I remembered some of the attitudes this friend has had throughout my relationship with my boyfriend. Every time I'm looking for a gift for him, she gives me options, which are always welcome because she knows him. But the problem arises when she emphasizes things like, "I know him well, I knew him before you did, I know what he likes best," or "It's obvious you don't pay attention to him, he likes this other thing, take my advice, he and I are inseparable." What really bothers me is that every time she has the chance, she repeats something like, "No! He doesn't tell you anything because you're his girlfriend, and he probably thinks you're going to judge him. He does judge me, though. He tells me everything because I'm his best friend, and he tells me everything in great detail, and that's why I'm telling you everything he says so we can have this communication, you know, boyfriend-girlfriend communication."

And it certainly bothers me. My boyfriend and I have great communication, and he's very private, even with his parents. He hardly tells them anything; they only found out about certain things because they asked me directly. Otherwise, they wouldn't have known at all.

The last straw was when she started asking him for details about our intimate relationships. That's when the only "serious" argument with my boyfriend happened. He hadn't actually said anything I hadn't already said in jokes and conversations, and then my friend told me that my boyfriend had told her about our first time together.

I know perfectly well I'm not exaggerating about this last point, but I just wanted to give you some context about how I interact with this mutual friend.

Am I exaggerating, or am I actually becoming possessive?

There's something I omitted mentioning and until now I think maybe it's important.

Yesterday when I was talking to my boyfriend about the whole aforementioned matter, I started the conversation with something our friend said when we had only been a couple for a few weeks. I said, "Do you remember when our friend asked what you would have to do or what would have to happen for this relationship to end?" He said yes, he remembered, and that we had ignored her question due to time constraints, and anyway, that conversation happened the same day we became a couple; we both made our "non-negotiables" clear, like infidelity, disrespect, etc. And this is where I come back to that point and answered that old question: a reason why this relationship could end is because of her. Everything you all already know. He made it clear that he would be much more attentive to those details and would act accordingly to avoid making me feel bad. But once again, my mind still keeps thinking that I'm on the verge of making myself look like a jealous and possessive person, something I definitely wouldn't want.

I also want to clarify some points regarding my boyfriend and our friend. He is quite reserved, not shy, but very reserved when it comes to personal information. He's one of those people you can talk to about anything without taboos, without feeling judged, and you enjoy those chats. Our friend is someone who talks about everything explicitly, from what she ate for breakfast to what position the last man she was with put her in; she talks about everything and generally with the whole friend group, not just my boyfriend. She also tends to redirect a conversation that's happening in the group to something that happened to her or something she did related to the topic being discussed at the moment. She's a very anxious person, to the point of behaving like a little girl to do simple things like talking to a stranger, dealing with government paperwork, or simply being a functional adult. I've made it clear to her, nicely and not so nicely, that it's something she needs to handle on her own or with a psychologist or something, because when these situations arise, it's quite irritating to have a 26-year-old woman, almost 90 kg (198 lbs), clinging to your arm and trembling like a huge Chihuahua dog behind you. I've told her this last part directly, just as I've said it here; it's something that both my boyfriend and I, and the rest of the friend group, all agree on.

And regarding whether I'm sure there hasn't been any kind of physical/romantic relationship between my boyfriend and this friend, the answer is no, it's been nothing more than friendship. I can assure this for several reasons. One of them is hygiene. My boyfriend is very finicky about hygiene, and I'm just as dramatic about hygiene as he is. However, our friend has questionable hygiene, something my boyfriend agrees with me on (and it's not to insult her, but we've even spent a whole week living with her on school/work trips, and seriously, seriously, she's a person of questionable hygiene). Another reason apart from hygiene is their interaction. Even though this friend knew him before I did, they really didn't interact much more than during university classes. When the three of us were in a classroom together, for the first few months my boyfriend didn't even seem to be part of the group; he was just forcibly included by this friend because she saw that he was "alone". Over time, he and I had much more affinity and we stayed alone many times, where I discovered many things about him personally, which was an achievement because, I insist, he's too reserved. Simple things like how many siblings he has or how many people are in your family, if he's ever had a girlfriend or dates. That's when I began to know him in depth and he began to trust the rest of the group. This triggered him talking a bit more about himself, but still very vague things, and well, from there a friendship developed and then a relationship. He is currently much more open than before, but only with me. But to find out something very specific, I have to ask; it's not like he just tells you out of the blue, I have to ask directly.