I agree that it seems to be a control thing, just based on a current example from my own life. A girl I go to university with (2.5 years older than me) was chasing me down most of last month, but I'm not attracted to her and have a girlfriend, so I stayed very distant. In the last week or so she's started on a guy a year younger than me - almost 4 years younger than she is (she's 22, he's 18).
Nothing wrong with it of course, but she's told me repeatedly how hurt she was by her ex (he was cheating on her for pretty much their entire relationship) and just has extremely low self-esteem in general. She goes for these younger guys because she feels she can control them. So my advice, and I'm basing this solely on my own experience, is to check for some sort of previous guy-related trauma in her life. If it's there, then that could well be the reason.