AITAH for "cheating" on my (ex)gf?

tl;dr — there was a miscommunication and i assumed me and my gf were no longer exclusive during a break because she dodged the whole question, and so i hooked up with someone else. now she thinks i cheated.

so i (15F) was on and off with my exgf (15F) for 10, almost 11 months. it's not my first relationship but is definitely the first relationship i've taken seriously considering my age. it was overall quite toxic — she had avoidant commitment issues and i had a very anxious and preoccupied attachment style. it was like my body would literally reject her, i'd have frequent panic attacks and relapses and use marijuana/alcohol daily to try drowning out the anxiety. this is only relevant because i want you to understand our relationship in case it sways your judgement.

she ended up ignoring me for like a full day even tho she was active on every social — this worried me because there's been countless times where she's assured me i'm the only one when i definitely wasn't, blown me off to hookup with someone else, and lied straight to my face about her relationships and sexual history with people. assuming she was cheating, i said we should break up because all my friends told me to (they all despise her). we ended up "working it out" and came to the conclusion of a break instead. we both needed it. the commitment was stressing her out and the anxiety was draining my health.

later that day i brought up loyalty. i said to her i wanted to be the only one she was talking to right now, obviously referencing exclusivity, to which she replied "i talk to my friends". i thought that was weird to say, so i specified, and all she said was "yeh". she knows that word pisses me off because there's such a lack of effort and respect — and it's like she tried to get under my skin. i told her to stop doing this to me and to just be honest because it's the only thing i've ever asked her to do, and she just left it on seen instead of saying anything even remotely comforting. i left it and she didn't speak to me again for 2 days. within this 2 days i started snapping back some boys because i thought i might as well; if she was dodging loyalty, so would i. so anyway, i end up hooking up with one of them (15M). i didn't see it as cheating because we were on a break and she wasn't being clear on whether we were still sexually exclusive.

she found out and started absolutely thrashing me, calling me a cheater and saying i always blame her for everything and that i did "the one thing i told her not to do". i said she's done this to me so many times, and her excuse? "but they weren't real hoes for me it was a boredom thing". her points were ridiculous and she purposefully dodged every good point i made. i ended up sending her voice messages just trying to convey my argument in a calm, clear way. she responded the next morning "idk why you've sent vn, i can't listen i'm at work". i told her to just listen after work, i didn't care when she listened. she ignored that and unadded me instead, which i guess stung after i put effort into sending voicenotes, but whatever. she's now telling everyone i cheated but i don't think i did. AITAH?