you should confront her about it. just ignoring the situation and letting it play out will not accomplish anything. tell her you think she is hitting on someone she knows you like and then talk to her about it.
It actually depends on how they do it. If it's in a really bad situation, you should ask why they did it. Depending on the answer, you should think about if they really are a best friend. If it's not that bad, you might get over it. Think about it.
If your upset about it, talk to your friend. Say that you think your being replaced. But remember, it's not all about you. She/he can have more than 1 best friend. Who knows, maybe your not the only one.
Then the best friend should tell the boy that this girl likes him and after he knows the girl likes him the girl should go over and ask him out if you like him that much or make a conversataion with him so he knows that the girl really does like him and that's when they start off a relationship.
Well, if your best friend likes your boyfriend, then I really think you shouldn't date him. If your best friend just doesn't like him, then you should just date him. I mean, does it really matter what your best friend thinks? She should like you no matter who you date.