Not to downplay any concerns here, but I wonder if perhaps her friend is just trying to act a certain way, according to the latest trends?
I’m sure I’m wrong in some cases, but the first thought that usually pops into my head when I hear about a female teenage bisexual is to first put the word “bisexual” in quotes. Not because I think bisexual attraction doesn’t exist, but because it seems to be more of a fad these days than any sort of true attraction. As in, probably 95% of the young women who claim to be bi really aren’t at all; they’re just trying to act in a way that they think is sexy, because society in the past 15 years at least has been promoting lesbian action among heterosexual women as something that turns men on. And since the age of the sexualization of children is getting lower and lower, it’s not likely that 14 year-old girls will be immune to it.
I guess my point is, maybe this will blow over quickly. Hopefully this friend is just acting out, and a firm “knock it off” will set her straight. If her friend respects it, there’s no reason they can’t continue the friendship.