As long as she is living with her mother (and she is, right?) then all bets are off. The only way things are get going to get better is if there is a literal separation- some kind of distance. Of course, her mother does not know what she is talking about. Yes. There are people who claim they can pray away the gay. But this amounts to repression, not a change of orientation.
Love and attraction has it's own rules and laws. And these are matters of the heart. Love and desire, attraction and longing are like A big wide river. You just can't change its direction.
Be the love you seek.