Best friend issues! don’t know what to do

My best friend and I have been incredibly close for a few years. She’s genuinely been “my person,” but for probably the last 5-ish months I’ve felt like she hasn’t been a very good friend to me, and I can’t work out whether I’m justified in feeling that way or whether I’ve let resentment build up because I’m terrible at confronting things.
We used to live together with another girl. Me and the other girl were never particularly close, but my best friend got on with her fine.
Me and my best friend have always had a very relaxed shared-clothes thing. She wears my stuff, I wear hers, neither of us normally cares. At one point she was away from the house for about 2 months and I definitely took advantage of the arrangement a little and borrowed quite a few things. But I was obviously going to return everything, and she knew I was wearing them — I’d post a picture and she’d literally reply joking about me wearing her shirt/jacket/etc.
Towards the end of us living together, the other housemate went into my room while I was out and spent an hour going through my things looking for my best friend’s clothes. My best friend was on FaceTime with her while she did it.
Afterwards, the housemate messaged me saying basically, “Me and [best friend] have issues with you that we need to talk about.”
This hit a massive nerve for me because when I was about 17 I had a horrible situation where two friends sat me down, listed everything they disliked about me, and then stopped being friends with me. My best friend knows that happened and knows how much it affected me.
My best friend immediately messaged me separately saying essentially, “I don’t have beef with you, she shouldn’t have worded it like that, everything’s okay. Maybe we should just stop sharing clothes for now.”
So from my perspective, I thought the other housemate had basically tried to manufacture drama between us. My relationship with her completely broke down after that and we barely spoke for the rest of the time we lived together.
Since then, though, there have been lots of small things with my best friend that have made me question things.
Her family have always treated me like family and joked that I’m basically another daughter. But I’ve asked to stay at her house a couple of times and she’s told me her parents didn’t want anyone staying, or that they’d only let me stay one night. Then when I’ve actually been there, one of her parents has casually said something like, “Why don’t you stay another night?” which made me wonder whether her parents were ever the reason in the first place.
Another example: she’s currently having relationship problems. She told me what was happening and I felt like I could see a very obvious solution, so I kept giving her advice about it. She got frustrated and basically told me I was completely wrong and needed to stop pushing it.
I realised I’d overstepped, so I sent her a little care package and an apology saying that I loved her, wanted the best for her, was sorry for pushing my opinion, and that I’d support her regardless.
She replied really lovingly, saying she loved me even when we disagreed and thanking me for everything. So I thought, okay, we’re fine.
The part that’s really upsetting me now is that I’m currently going through by far the worst breakup I’ve ever experienced. I’m genuinely devastated and struggling quite badly with it, and she knows that.
The day my ex and I officially went no-contact, she didn’t reply to me for well over a day.
Then a couple of days ago I messaged her saying I was having a really anxious day and asked whether she might be free to see me briefly on her lunch break or after work.
She still hasn’t replied to that message.
She did send me something unrelated on Snapchat, and because I was hurt I gave quite a dry reply. She then asked, “Are you okay? I’m not mad at you.”
And I honestly don’t know how I’m supposed to feel about any of this.
Whenever she has been heartbroken, upset, anxious, having relationship problems, family problems, anything — if she has needed me, I have dropped things and gone to her. I don’t expect someone to be available 24/7 and obviously people have their own lives, but I feel like if my best friend messaged me saying, “I’m really anxious today, can I see you?” while going through a devastating breakup, I couldn’t imagine just ignoring the message for days.
At the same time, I know I have a bad habit of avoiding difficult conversations. I let little things bother me, don’t say anything because I don’t want conflict, and eventually I reach a point where I want to completely cut somebody off. I’ve done that before and I really don’t want to repeat that pattern.
She’s been my best friend for years. Six months of weirdness doesn’t feel like enough reason to throw away the entire friendship, especially when there have also been loads of genuinely loving and good moments between us.
But I keep coming back to the same thought: would my best friend actually treat me like this?
I feel like I’m constantly giving her the benefit of the doubt while also feeling increasingly unwanted and unsupported.
Do I need to actually sit her down and tell her all of this before deciding anything? Or is the fact that I even feel this consistently unsupported a sign that the friendship has changed?
I’d especially appreciate perspectives from people who have had long-term friendships go through a rough period without immediately ending them.