@Everest,
come on man from my analysis of the situation either of these could be true:
1: Lust: u've always entertained the thought of banging her and probably if u want to be honest u've molested your self over the same thought...
2: she is revealing to you.. showing u en revealing all the curvatures may be she is into you.. and your the one who is repulsing ur self.
3: Women are naturally jealous of each other.. may be the two of then have some sort of fetish or a pact that they would want to twanga the same man or have a kamsort of three sum u never know.
4: it could be a trap
My advice follow ur instinct and not ur manhood. If they tell you this a gud hit then my bratha ur wasting time else get one of us to take one for the team on ur behalf.