Why do I get triggered?

So I haven't been on here in a while because someone on here was being a little rude to me but heyyy everyone. I have been happy for the most part and I'm trying to put my past completely behind me and so far that's been going well but when I was at orientation I met this really nice girl and she had so many scars and I got super triggered and still am triggered. I'm happy and I don't need to self harm for punishment like I did before now it's just a random feeling when I see scars or fresh wounds. I don't know why or what to do because if we hang out I'm just gonna be triggered every time which isn't a good idea but I'm not just gonna stay away from her because she should feel comfortable showing her scars whenever and wherever so I'm happy she's comfortable but what would I kinda do to not get triggered.