WickedElphie
Bottom line, if she's not going to make the commitment to you and to practicing... then she doesn't deserve the chance to be in the competition.
I know being that she is your best friend and it might make this hard, but if she isn't going to put in the work that you put do or the that someone else that WANTS to be in this competition and will practice their butt off, then you have to replace her.
It might not seem fair to her, but in the real world it's the fairest of the fair. If she was in a professional production, if she didn't practice she'd be fired in a heartbeat.
Indeed. But another fact of the real theatre world is that if she's screwing the director and/or is the director/producer/writer's best friend, she'll keep the part and you'll have to suck it up.
Sorry. I'm a callous b***h. I wasn't calling your friend a slut, I promise.
But yeah, have a come to Jesus meeting with her and your director and her mother if need be. But also keep in mind the level of competition that you're at and how much it's going to affect your career should you choose to have one. For example, I was really angry at my seventh-grade duet acting partner because he wouldn't memorize his lines and we never broke at a competition, but the fact of the matter is that he's going one way with his life and I'm going another and basically nothing before tenth grade counts, unless you were the lead in a huge show as a freshman.