hm4m, I'm guessing that's a reference to the movie, in which the person answering the ad that starts "SWF" (single white female) ends up fearing for her life because of the nature of the new roommate's increasingly obsessive interest in her, and not any reflection on anything racial.

Joe, I'm surprised that your girlfriend would hitch her star to the wagon of someone so many decades younger; but it does sound like this person has been deeply flattering to her ego. Should the young woman become disillusioned at some point, or find somewhere else to re-invest her attention, your girlfriend might end up without a paddle on the creek as far as a living situation is concerned.

I don't know if there's a particular name for the behavior, but it does sound a bit manipulative, and cavalier .. and the younger we are sometimes, the more guiltlessly we are able to toy with others' emotions, because we haven't as often experienced the sting of heartbreak. At least that's been my experience.