Leah & Ange,
The best thing to do is to start talking about school and how big girls use a cup. Maybe you could find a really pretty cup with her name in rhinestones on it or something. Just say that baba's are not allowed at school. Hopefully, this won't make her dislike school, but just get her reaction. Also tell her that if she wants to have pretty teeth, she's going to have to put the bottle down.