She’s seeing someone else but lies to me about it? What’s the point in that?

So me (26M) and my ex (25F) broke up in February, after 4 years. But of course are still friends, in fact we are best friends and spend time together quite a bit, she stays over and vice versa..

So for a few months now, I’ve heard through the grape vine and have been shown pictures of her and this other guy… (something I don’t understand is when your friends like to forget that things like this aren’t any of their business, but make it theirs anyway)

I want to start off with explaining that I don’t mind at all who she sees or what she does with other people. I’m not the type of person to care about something like this when I’m an open and honest person. She’s also a sex worker and has been way before we started dating. Please note that I didn’t meet her through sex work haha, I met her at a mutual friends house party back in 2014! So we’ve known each other for almost a decade and as much as I love her and genuinely see her as the love of my life, I want her to be happy and experience love and joy in all aspects. Whether it’s working, or seeing someone else, seeing me or whatever falls under that category..

She can tell me about the men she sleeps with at work and she knows how accepting and supportive I am.

So when she hides a pretty big part of her dating life from me and then lies to me about it when I confront her, it confuses me?… She can easily lay in my arms in bed and tell me she loves me and still wants to be with me and doesn’t want anyone else, but then has a guy who is uploading pictures of them both publicly which means they’re obviously or almost exclusive, it frustrates me. I asked her “why didn’t you tell me you had a boyfriend?” And her only reply was “I promise you that I don’t and I’ve told him to delete the pictures because it makes it look like we’re a couple”… he hasn’t deleted them lol which I only assume that she lied to me about telling him that.

The only things that irritates me about this is that she’s lying to me about this, but has no reason to? I don’t understand the motive behind not being honest when I don’t mind. HOWEVER, the other thing is that I don’t know if he knows what she’s doing when she’s not with him. I know that she wouldn’t have told him about her being a sex worker, barely anyone knows. And I don’t know if he knows that she’s still coming over to mine. It puts stress on me knowing that she could potentially be fucking around with this guys feelings and if he doesn’t know, then I’m far from okay with that…

Take into note that she is an avoidant attachment, and it worries me that she’s just gonna end up hurting herself..

I don’t know what to think of this, I don’t really know what I’m trying to ask. I guess I’m hoping someone has maybe experience something similar or can give me their perspective on what they think could be happening…