Man, that sucks. I don't really have any good advice other that sharing articles with your mom about how stuttering can't be cured. And hopefully you can find an article about how going to a therapist who you don't like and isn't doing anything won't help you. She needs to adjust her attitude. Are your parents religious? Maybe you could point out the prophet Moses had a stutter and that didn't stop him from uniting his people and escaping the pharoh.