Or, it could mean she still has a thing for him. Maybe she is jealous...wants him back...wants to know if he's dating anyone or what he's up to...
This is what I believe! She's not over him yet...she's keeping close tabs on him. I don't think this makes her crazy, I just think it means that she's not over this guy yet.
Up until a few months ago (for a couple years time), my husband's EX(who is beyond crazy!) followed him around at the forum he frequents, she was always in the threads that we would post in. This forum lets you see who's viewing it. Finally I said something about it and miraculously she went away. I'm no fool, she was still hung up on him and this was the only way she could see what he was up to.