Had a regular girl for a few months but I was non-committal and I guess she had enough and stopped talking to me for a few weeks.

This weekend I've come to find that she has a new guy, which has spun me out a bit but whatever.

What's annoyed me is that she's bringing this guy to my local bar to rub it in my face. He has no idea of our history, but she sits there with this fucking smirk on her face.

What would be the best way to act towards her/them? It looks like I can't avoid them anytime soon.