To get a real solution to this we need to analyze why she'd listen to him over you, so first let's examine what elements come into play here:
1) Women work by backwards rationalization, meaning whenever a situation comes they don't analyze things logically and then act according to that, they act and then try to add logic to rationalize their answer (and let's be real, most of the time there's really no logic that could possibly explain it.)
2) He has comfort - keep in mind, your skill sets better than his.
3) If you're doing it right you have both comfort and attraction. (Be sure you understand the logistics of proximity here, as you should know if they're beta; and they are, they won't say shit about you to your face, so the moment that you leave the group he'll start talking crap, but if you REALLY do need to leave I'd recommend do some pawning so that even while you're gone you'll have people maintaining your frame without actually having to be there [be careful though because if you leave people who you do not have enough social proof he'll destroy your frame with them as well] so even if he does talk crap about you, she hears more positive stuff about you from your friends you left in the set, than bad stuff from her friend, and soon enough, she'll realize he's just a hater.
4) "The strongest drive known to humanity is not survival, but familiarity.", by this law, you immediately have less rapport than the wannabe suitor who got friend-zoned, unless you build the frame of a "long lost friend who friend-zoned the girl." (do this via the help of the cat-string theory, role reversal, and friendly, yet not too interested in conversation with her so much as the group, whilst flirting with her "unintentionally
") and after she starts qualifying herself to you, it's time to pay her some attention. Isolate her. Before you try to isolate her, get her to admit to being somewhat adventurous, or to demonstrate it, that way if the otherwise gay friend tries to object, the only thing you have to do is remind her of how adventurous/ open-minded she is, and subtly hint the fact that her friend is holding her back, or being a hypocrite, then disqualify her for allowing herself to be held back by others, heck you can even sprinkle a deeper compliment here (ex. "My bad, I figured you were a more free-willed person, but I'm not much for taking care of people who can't make their own choices.", at this point your body language should be displaying the fact that you're about to bounce, at this point if you've been playing the game hard enough, she'll be qualifying herself to you as you're about to leave.) (If you're the alpha of the group, which you should be in the situation described, the best way to get her to be adventurous, is to get the entire group to be adventurous).
5) How did you open. How you open defines the logistics of the group right-away. If it's a two set, wait for her to excuse herself (make sure you're hanging out with other people so you don't seem like a creeper.) and when the opportunity arises, make sure you open the potential friend zoner, and open a good conversation with him, captivate his interest, and that way when she returns she's being shut out, make sure you at least sorta notify her existence, and after she walks away because she's being blocked out by her friend, you've successfully destroyed her faith in her friend (she just got ignored by him for the sake of this random guy) and you come up to her, like, "Hey you're x right?" Open the set, and after a while, say something like this "Wow, you're pretty awesome, I don't know why "name of the FZoner" was ignoring you earlier." Boom, you've successfully destroyed her faith in him as a good friend and with that all credibility he would have had if he tries speaking out against you, after all, YOU didn't ignore her, HE did.
Good luck with this, a lot of this I took from my own experience (accident or not
).
CHAT
I've seriously ran into this 4 or 5 times. 