I am [18M], she is [18F]. We've been going out for 5 months. Not long ago my GF went to a party hosted by one of her close friends that happened to be her ex's cousin. One of her female friends contacted me to explain that she thought she heard her and her ex chatting shit about me and we're together for most of the party.
Her Ex was toxic and abusive, most of the time I've seen or heard them interact the interactions were heated and short. From my knowledge she hates him. I spoke to 3 people from the party, 2 of them are her female friends but one of them is pretty mean to her quite regularly. The other friend is someone I don't know, but have heard them to be trustworthy. The third person is one of my friends that had been there too. I'm told a different story from him who said they'd only spoke for 10 mins and had been in the same friend group a few times in that party. The other story is that she'd been with him for most of the night and had spoke quite a lot. My GF says similar things to my friend. My GF showed me photos of the party where she was with other people that she had said she'd been with the whole time.
I trust my GF, but these friends surprise me by coming out of the blue and saying that her and her ex were together for most of the night despite not being in contact and showing hatred for eachother prior to the night. My GF only told me about their interaction after I had confronted her about it, she said that she'd considered mentioning it a few times but she was scared of my reaction to it.
Currently at a standstill, no way to prove anything that isn't just other people talking to me about the night. I've been told different stories from 3 people who were there now, my own friend backing up my GF, and her friends saying she was with her ex. (Also, just to note, the one that contacted me then referred me to the other person, the one I don't know very well. I got a very very similar story from them)
My GF hasn't acted any way to say she doesn't still love me, or that I'm a "pr*ck" as she was allegedly overheard agreeing with.
Don't know what to do, would love some advice on how to proceed. Any questions welcome
(Sorry if this is jumbled, there's a lot of information to get through)