<human>: Currently in a long distance relationship with my girlfriend, it's been 4 months. Before me, she briefly was with someone else while she loved me, trying to forget me thinking I would never love her.
He got upset at her, started swearing and hurt her, guilted her and talked to his friends about her. One of them called her a bitch and asked him to tell her, which he did ("oh, random told me to tell you you're a bitch").

They pretty much stopped to talk for around 2-3 months. Now, to be clear, I hate that guy. She started talking to him again recently and never told me until 2 weeks later. She probably thought I would get upset and when I learned about it, she tried to comfort me saying she would never have feelings for him anymore and that it was an error to ever be with him, so I trust her about that. He hurts her but she keeps going back to him.
I pretty much asked her to stop talking to him because it was making me uncomfortable and she said it was hard for her to cut off friends, which again, I believe because I know her. But he keeps making mistakes. Recently he started talking behind my back to her, calling me immature and things like that to make himself look better, I guess. She told me 2 days later and showed me what he said but never what she answered him. I asked her to show me the full conversation about me and she always said "no, I don't want to" not giving any other reason.
Now it's been 2 weeks and today I asked again because the subject was brought up. She had to delete her conversations for some legit reason but said she would keep their conversation to "maybe" show me one day. Just 30 minutes ago, she deleted all of these, the one with him included and therefore will never show me.

How am I supposed to feel about that? Am I overreacting if I feel betrayed?

Give me the gist of the text in a nutshell
<bot>: my girlfriend keeps talking to her ex, they talked about me, showed part of it but never wanted to show it entirely and now deleted the conversation.