So you can either spend time worrying if some man you don't know will have his feelings hurt if you sleep with a woman who wants you, or you can sleep with a woman who wants you and figure that if someone is upset about her for sleeping with someone else, well, that's between that person and her.And if she was REALLY his, there's not a thing you could've done to get her... And hey, if she DOES give you the slip for some other cat, you can take that as strong evidence that either you weren't doing things right with her, or she wasn't the kind of girl who believes much in loyalty and fidelity, or you're dealing with some combination thereof (usually it's some combination thereof).
The question is not what you should do, but why you have chosen to like a guy who is unavailable.
Some girls think that love "just happens" -and if it's with the wrong guy, they can't help it.
Focusing on a friend's guy is a little closer to home: If he breaks up with her, he's more likely than the suddenly single Brad Pitt to go for you.
The final and saddest reason a girl might choose a guy who's with someone else is to prove her power.
This arrangement would generally be called a friend with benefits, or a fuck buddy, or a romantic friendship, or perhaps even a relationship—with “no strings attached.” But let’s be real: There are always strings, aren’t there?