Quote:
Your reaction should depend on what you want, and what kind of girl she is.
If you're into her and she means something to you, then you have to make her feel that. If she isn't, then just be happy to continue nailing her. In other words, who do you want to be? The guy that she relies on day in and day out for anything and everything she thinks she needs? Or the guy she has fuck the shit out of her when she's single or shit is gone south with her ex or anyone else for that matter.
If you want the former, she will choose the guy who makes her feel more. Women always do.
True in general, but doesn't apply to this situation - he should not react. There are other ways to make her feel special, not by communicating to her that he's worried and "thinks" her ex is trying to get back into her life. This might not even be about her ex, tho it does sound so.
@DasaniMal: show that you care, but don't get hung up on a status update she posted on facebook (correct me if I'm wrong and she actually posted online to YOU in person. As long as she doesn't talk to you about it, don't react).