Bit of advice dealing with my ex?

If it's really bothering you this much, maybe you should consider the idea of hanging out with a new group of friends. Being with these people and this girl will only continue to make you sad and watch them together. You said you wanted to give them space and everything but how about you give yourself space, because you're emotions are all that should matter right now. She's moved on buddy, I know it's hard to swallow that fact but you need to. Get away by yourself for a while, find a hobby that takes up all of your time and run with it. Until you can get over her, hanging out with that group of friends and talking about her isn't going to help.