my girlfriend flirts online and i love her to death, what do i do?

[Cris]

I treat her like gold, don't cheat and never will. She has a profile on POF with NO pictures and old info and I got this message the other day from this guy telling me she messaged him asking to give head. At this point, we weren't together we were broken up. But he told me he could tell by the way she talked she was all talk no action, almost like she was scared or knew she was doing something wrong. He said they never met up and classified her as a harmless flirt, a flirtacious person. He said he thinks she may just have a fetish or fantasy of giving head. What I did find though, is she added this guy on facebook and another guy from POF just so they could see what she looked like. And the other thing is, shes friends with her ex on facebook and likes her timeline posts about phrases in life. This makes me think she misses her ex and they talk. Of course she denied being on POF and she said she doesn't miss her ex and her ex doesn't talk to her. (her ex has a girlfriend)
I still love her and wish I didn't have to give up on her. Shes gorgeous and can be so great some days. I think she may have a lying problem and doesn't know what shes doing because its an illness. What do I do?
Im scared one day she will maybe meet a person if we happen to be on a break. But I do believe deep down, shed never meet anyone in person if we were together. She always told me she doesn't think online things are cheating if its only talking, but she would never meet anyone if shes in a relationship.