availability policy Options

[batman]

One of my friends thinks that anything's fair game as long as there are no kids involved, i.e. she could flirt with a married man so long as he doesn't have children with his wife.

Anyways, X and Y hang out a lot. A lot, a lot. Like all day and all night, a lot. Y has (or had,... it's pretty unclear) a girlfriend, but barely mentions her name. X just had an epiphany and realizes that she really, really likes Y. X doesn't really know what to do. M (me) tells her to bring up the girlfriend to see where they stand. X doesn't want to. X plans to just keep spending a lot of time with Y. M doesn't like that plan.

The way I figure... she already likes him so much and she doesn't really know where they stand. He has this girlfriend of about a year or so, but she says he's only mentioned her once in the entire time she's known him. The more time she spends with him not knowing how things are between them, the more she's gonna like him, right?

Meh. I'm telling her to back off a bit until she knows what's up, but my other friend's telling her to go for it.

What's your policy about dating/flirting/etc with someone who's technically 'unavailable?'