I remember reading a psychology paper about what you are observing. I can't link the article, but to sum it up it essentially stated that women, or men, with a particular set of issues often are attracted to and fall into relationships with those who would be lower in empathy and are more self focused (narcissists, etc.). I could easily see how a clingy, unstable and insecure women would crave the attention and validation of a man who does not provide her much love or support. I think those with histrionic or borderlines might fall into this category, as the majority of those with these disorders are by and large female.
I have a friend who I would honestly say is a bit of a narcissist, albeit it isn't that bad to the point where no one likes him. Anyway, he has this woman who is a sort of FWB that he has sex with whenever he feels like it. He will literally just text her that he is coming over and he goes and does his thing. He offers her very little in regards to attention and it is quite apparent that is all she is to him, yet she pursues him relentlessly, texting him entire pages worth of crazy "love". I've actually met her and within a few minutes I could tell that there were some issues, as she came across as very immature for her age. I actually kind of feel bad for her but given what I've observed and heard he hasn't really done much to make her think that he wants anything more than that from her.
Now, I guarantee that if this woman was to meet a guy who had good intentions with her she would grow bored of him extremely quickly and lose interest. Crazy women are often a result of an unstable upbringing, which this young woman had, and by and large are drawn far more often to "bad boys".
