Re: borderline bitter
B's first comment means that she thinks the girl A is going on a date with is controlling the relationship (she is wearing the pants) and her "suggestion" is that he wear girl-type clothes (specifically, rather slutty clothes).
Originally Posted by maiabulela
When someone is bitter, they are angry and resentful. A is saying that B is showing her bitterness -- or at least coming very close to sounding like she is bitter by coming right up to the edge, or the border, of bitterness.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.