What should I do about this girl?

Alright so I have been talking to this girl for about 2 months now. Shes actually one of my good friends sisters. I have known her for about a year now but just started talking to her as more than friends recently. We get labeled as boyfriend and girlfriend by all our friends but we really dont have a label. We have talked about our relationship at first and decided that we didnt want to rush into anything for the reason that her brother and her as well are good friends with me and we didnt want to ruin that by rushing into things. Everything has been good, we do everything a couple dating would do. The problem is she broke up with her boyfriend a few months ago and shes still not over him. She always brings up that she’s still really heart broken and has been honest with me about it and said that is why she hasnt comitted to a serious relationship with me. The wierd thing is that she is all lovey dovey when shes with me but she always brings it up when were on the phone or texting. I really do like this girl, but am I just setting myself up for dissapointment in the long run? Should I leave our relationship at where it’s at and just continue as a friendship before I fall for her even more? Am I wasting my time? help