Hey Tom,
And I know that you could say that maybe her boyfriend treats her badly or isn't enough of a man but these seem more like justifications than actual reasons.
Chase never suggests that you insinuate anything about what a girl's boyfriend is or isn't doing, and he isn't saying that you should use these as justification for sleeping with her. The one thing he does know, and that is true, is that a girl will
not cheat on you if you are taking care of all of her needs. If you are her best friend, her lover, and (potentially) her provider, then she will not have a roll in the hay with a guy and risk destroying what she has with you. And if you're really everything she's ever dreamed about, she simply won't even consider it.
So when a girl has a boyfriend and is still willing to sleep with you, it should be a large indicator that the boyfriend is not fulfilling all of her needs. And I think one of the most eye-opening quotes from Chase's articles on girls with boyfriends was this one:
...the way I see it, there's always some guy, SOMEWHERE who's going to be angry you're sleeping with a girl - whether he's her boyfriend, her ex-boyfriend, her husband, or just some guy who's already "called dibs" on her and you moved faster, it doesn't matter - somebody somewhere is upset that you're with "his" girl. 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.
Remember, you should
never treat a girl like she is "yours." Even if she is your girlfriend. A girl is never completely
yours -- she is not your "property", and it is your responsibility as the man to continue to provide her with what she needs... or face the facts that she might go elsewhere to get those needs fulfilled.
This is my point of a view, and personally, I think it's a good way to see things. When you have this mindset, it will never let you get "too" comfortable with your girl and actually end up
being that guy who gets cheated on. It keeps you squarely in check and smacks you in the face when you think otherwise.
Always be the man she's hoping you'll continue to always be.
Cheers,
Franco