Unofficial relationship, girl flirted toooo much with a guy

[logarithm]

Hey guys, haven't been here for a while...
A month ago picked up a girl. We are leaving the country within a month and will break up then for sure, but now we're still in some kind of relationship, even though unofficially (she sleeps regularly at my place, spend lots of time together, etc). We hang out with other people too, even though presumably don't make out with them. However, yesterday we attended a party, dances and stuff, both of us flirted, which is fine, but...
At the end she went to some guy (he's cool, amazing dancer, has good game too) to talk with him for a while and he started gaming her - hold her hand while talking, then showing some moves slowly (there wasn't music any more) and stuff like that. Since we aren't officially together, I didn't interrupt and went to chat with friends. However, it lasted for about 20min and finally went there to check the situation, kept cool, chatted for a while and said we should leave (the girl is a neighbour). She said just a minute, so they finished the 'lesson', but it took nearly 5. When we left, I told her that I as going to leave alone any moment now (which was true) and that this shouldn't happen again. She looked kinda embarrassed and apologised, noticed that I'm upset and behaved nice (she does in general). However, obviously she was interested in the guy.
Now I'm not sure whether to break up and get a new girl (I have options), suggest her to be in an open relationship or leave the yesterday's accident for good.


Tonight there will be another party and all of us will be there, so if you have any suggestions, will be glad to see them. Haven't been in this situation before.

 

[marmel75]

She's not your girlfriend, she is leaving, why do you care?

 

[logarithm]

I don't like long relationships in general, few weeks/months and then break up because of some good reason (like leaving town) and still keeping the vibe and only nice memories works best for me. The girl is supposed to be my girl actually, even though not all of our friends know about it. If she was just some sex/make out buddy, wouldn't care at all obviously, would date other girls too.

 

[Greasy Pig]

Regardless of how casual or unofficial the relationship is, I think if she and you are at the same venue, it's grossly disrespectful to blatantly and openly act like she did.
If it happens again at the next party, just grab another girl and give your chick a taste of her own medicine.

 

[JohnChops]

Regardless of how casual or unofficial the relationship is, I think if she and you are at the same venue, it's grossly disrespectful to blatantly and openly act like she did.
If it happens again at the next party, just grab another girl and give your chick a taste of her own medicine.

This. And you guys arent really anything so why do you care? As marmel said.