So I've got a bit of a problem. My best friend's girlfriend has always had a bit of a crush on me, and has made mention of it several times in the past. Since she's utterly devoted to him and I didn't know her before they got together, it's never really been an issue beyond "whatever" to me.
In the last couple months she's been a lot more open to me and asking some advice about their relationship. Cool, I figured, I'm more than willing to help her, and by proxy my buddy, out if she needs it. This continues pretty steadily, and she becomes a bit more of my friend, though I still mostly just view her as his girlfriend. She comes by occasionally, usually with him, but sometimes just to hang out or whatever. I make dinner pretty often (I'm a cook), which she always claims is the best she eats.
Fuck her for all she's worth, but don't fall in love with her. She's not girlfriend material, for sure.
First talk to your friend, explain the situation. Do the reverse psych. cliché line "look if you don't want to, i won't see her..." , only if your feelings are strong.
If you go behind his back without talking, and it does get serious between you two, you will not be able to hide it anymore. Plus, such betrayals affect people the most.
She’s probably wanting you because of the excitement and drama it creates in her relationship, and she is turned on by the fact that she is possibly cheating on her bf. There are girls like this because there was some problematic manifestation from the relationship she had with her dad. For example, having a dad who wasn’t committed to the family can create this psychological inclination to pursue guys who aren’t committed to her, and find them attractive. Once she knows that her boyfriend is committed, she doesn’t find him attractive as much, on the other hand you create drama. Yet she knows the values of the relationship with her boyfriend so she is basically using you to get what she wants, excitement, and at the same time keeping her relationship.
Let me be as blunt as possible with you.
No matter what you do, you are running a 90% probability of losing this friendship. Drunk or not, you've already gone way too far.
I do not automatically agree with the other posters in this thread that she's probably rather flighty and looking for excitement, however, this is also a situation of "She did this WITH me, how can I trust she won't do this TO me?" Try to let her down lightly; something like "I'm sorry, but I just can't do this to [best friends name here]. I was drunk/not thinking clearly that night... I'm sorry, but I don't think we should hang out any more."
Bros before hoes