<human>: So I've met this really nice girl on tinder a few months ago. We met up a few times, and 3 months ago it got official. We're doing great! This is my first relationship, she already had one that ended in June. They've been together for 3 months, and in the first 2 months it all was really good according to her, but in the last month he got really abusive, verbally and physically. 

She's been bullied a lot in the past few years, so she was/is really insecure. So she stuck with him, even though he was so abusive. After a month she just broke down and left him. Since then they haven't had any contact as far as I know. And that's that.

But now the problem: I get jealous when I think about them being close. Even though it was just for 3 months, and now she hates him, because he was abusive in the end. She's told me they've never gone further than making out, and we've already had sex. So that's not the thing. I don't know what it is, there's no reason for me to be jealous about it and it's unfair towards her, because she can't help it. So I really don't want to be jealous, what are the best ways to not be jealous about it? 

I already talked about it with her, and she told me it was natural, and that I really shouldn't be jealous, but I know all of that. But it's not working.

Can you give me the gist of the text in a nutshell?
<bot>: I'm jealous of my gf's ex. Even though he was abusive and it didn't last very long. What should I do to not be jealous?