Fruit fly is also a slang word for a woman who likes to hang around gay men. I know a few fruit flies, and I actually find some of them really annoying. I really hate it when people want to be my friend for the sole reason that I'm gay, even though we have absolutely nothing in common. I like to make friends based on common interests and personality, not by who they date. Lots of fag hags and fruit flies are drawn to gay men because they want a male presence in their life, but are somehow threatened by heterosexual men. I know many a fruit fly who is secretly (but quite obviously) in love with her gay buddy; it just causes all kinds of problems with jealousy and frustration. Other fag hags have been brainwashed by popular culture to believe the gay therapist fallacy.
Don't get me wrong, I don't hate women or anything. I do have a lot of female friends, but we're friends because we like each other, not because they wanted to live some Hollywood fantasy and have a gay best friend.