Hi guys

My LTR told me that there is a friend in her 'clique' who she was dating before we got into a LTR. (8months ago)

After we got together she told him about me and it looked like he accepted it (she showed me the text messages) - all fine.

3 months into LTR she sends me a pissed voice message how this guy is trying it again bringing up old memories - still fine.

But then she described how this brought back her feelings for him. I was like wtf - you have feelings for another guy? I got pissed and caused a little drama but I managed to overcome this problem somehow.

Now 8 months into ltr - my friend, ltr and me went to a concert and coincidentally she sees him and turns to me: "omg omg why is he here." and she goes really red in her face - i took the situation with humor because he just ignored her.

Next day(texts she showed me): she texts him "sad, that you can't even say hi to me anymore and ignore me" and then he called her to clear things up. after that call i saw a lot of texting and especially teasing from his side - i know teasing is effective that's why i got pissed and tell is she fucking serious now? I thought this guy was history - I told her i don't ever want to hear/see his name again. she explained how it's hard to handle because he's in her "clique" - i understand that somewhat.

So I know I probably reacted bad but how to handle this in future? Will this guy produce more problems over time? How to handle it when they're out as a group? The feelings and that she's going red when she sees him is questionable but I know she is investing much into me - next week we are leaving together for travel for 4 weeks.

PS: 2 weeks ago they have been out as a group and he sat next to her and as he got drunk he started to be more "touchy" but she didn't react - that's what she told me (naive me)