I really don't care if she has a boyfriend usually. It's obvious that if she's into me, he's not satisfying her.
I've realized over the years that this could be the guys fault because he doesn't give her what she needs or it's the girls fault because she's an insatiable freak who doesn't belong in a relationship. Once you figure out which one of the two it is, I'd say then would be an okay time to determine whether or not you'd like a relationship. If she's insatiable, you can fuck her if you want but that'll probably be more drama than it's worth.
Emotionally healthy girls typically don't cheat on guys they are in
happy relationships with. I'm typically not a fan of anything serious with the relationship hoppers but that doesn't mean I won't enjoy sleeping with her a few times. If the girl is unhappy with her boyfriend, well you were just her way of ending it. Whether or not she really wants a relationship with you, I dunno.
You don't know this girl yet. To say she "checks all of your boxes" is pretty ignorant. Why don't you sleep with her a few times first before putting her in the girlfriend category? Actually see what type of girl she really is? Considering you didn't know she had a boyfriend yet.... Well, you're not ready for a relationship with her.
I wrote an article on my blog called The Girlfriend Checklist. It might be something that will be of value to you in this situation. Check it out!
