I would confront her about it, talk it out in a calm, and open way. I dated someone not over his ex, and his issues got in the way of him wanting to settle with anyone else after his break-up with her so best to get it out in the open now, and come to an understanding before investing more feelings in her. I fell for the guy, and unfortunately I'm not over him that much. I'm working on moving on, but honestly it affects me moving and meeting anyone else so I think that this is definitely an issue that she still has feelings for her ex. She could just be hanging out with you to stop crying and thinking about him, not really intending to commit to you or anything.

If it was me, I'd realize this person was not relationship ready and would either move on, or just remain as friends.

I would tread carefully on this. Your girlfriend has unresolved issues. Keep it light.

I think before she gets involved with anyone new she needs to be over the ex! A relationship when your not over the ex usually wont last because they are torn between old guy and new guy. I think you would be looking for hurt and pain to get involved at this time. Maybe wait it out longer and see if he heals and moves on then maybe. For now if I were you I would stay friends and leave it at that and even tell her how you feel about it too so she understands why you are not going to go beyond friends at this time. I hope this helps some.

I agree with luvmygirl, tread carefully, and keep things light until you have a better idea what is going on. I think it is challenging for many of us to get over the ex, not carry some baggage into future relationships, but you also need be careful that she doesn't string you along..