I’m a 25 M and my Girlfriend is 25 F, she’s been texting and sending selfies to other guy friends. I need advice.

Hello, Im fairly new here and this is my first serious relationship, whereas before Ive only had
one- night stands.

The situation:
Me and my GF are both in our mid 20s, we’ve been together for almost 8months now, and only last week I’ve noticed her snap score increase a LOT. She does have a lot of friends on Snapchat, but whereas before we were mutual BFFs now we aren’t anymore.
We’ve had an argument last week and from then on she asked for some ”me time” which I gave to her, that’s when her snap score increased while she started ignoring my texts / leaving me on read / or replying hours later.
We recently talked about it because I went to her place to break up with her since she’s been ignoring me while I clearly see she’s sending / receiving snaps from people. I have told her I have abandonment issues which I’ve carried from childhood, hence why I feel so strongly when I’m being ignored or left on read for almost a week. So we talked; she said the reason why she’s been ignoring me is cause I broke her trust by talking about our issues to our mutual friend. My GF is sometimes harsh with her words, like she’s closed off her heart sometimes due to pain from a previous relationship, I also cannot deal with how friendly she is to literally anyone, hence why I confided to our mutual friend who knows her for almost a decade; venting to her about the issues I have with my GF and sometimes asking for advice on how to deal with my GF. I told our mutual friend how Im not comfortable with her talking so often with her landlord and other guy friends, and apparently my GF found out I snitched to our mutual friend. This isn’t the first time I’ve confided to our mutual friend, and this is the 2nd time my GF found out.
She got upset since I talked about our privacy, which I can understand, but what am I supposed to do? I don’t feel emotionally secure with her anymore since the last 3 times I tried talking to her when I feel like this she just completely invalidated my feelings. My GF keeps saying Im overreacting, or how I shouldn’t worry since she’s told me she’s talking to this guy and this guy and her landlord and how I should ONLY be worried when she talks to this guy when she hasn’t told me. So I gave her the benefit of the doubt and decided to try again, maybe I was just overthinking it right?
However, literally an hour ago; she was in the shower and left her phone on the couch at her place. I couldn’t resist and I went through her snapchat. I saw that she’s mainly talking to 4 dudes (landlord and me included) and 2 female friends of her. None of us have the BFFs sign.
Here’s why Im here on reddit now.
I went through her dms on snapchat with the other 3 dudes, and saw she’s been sending selfies of herself to them and to me, nothing provocative. She’s never been the type to send provocative pictures. Her selfies mostly include face and sometimes whole body. Selfies she’s posted on messenger stories and some selfies she hasn’t posted.
Her landlord, who’s in his early or mid 30s, who’s still married and with kids seems the most flirty by the way he complimented her selfies and sending heart emojis even, saving a lot of her selfies she’s been sending. They’ve also been exchanging goodnight bitmoji stickers with each other during chat, whereas she hasn’t sent me any goodnight messages since last week. Hell, I don’t even know how else they’ve been interacting since snapchat deletes unsaved messages and snaps over the course of 24hrs.
I just feel VERY uncomfortable with how they’re interacting with each other. And I have told her this before, whereas she keeps saying the same thing, ”Im not hiding talking to him, you should only be worried when Im hiding it from you.” or ”Why would I? He’s married with kids. I’m just being friendly.”
It also makes me feel less special. Why does she need the feel to send selfies to other dudes? I thought I was the only one receiving these.

What should I do? Am I just overthinking too much? Can I really trust her that nothing is going on since she’s told me she’s talking to them prior to our argument last week? I am an overthinker, I admit. To me it feels like this landlord clearly wants to smash.
I’d like to hear your thoughts.. I really need help right now, as I don’t want to talk to our mutual friend about it. This issue has gotten so bad I sometimes can’t even sleep.