wow! I'm so sorry to hear that your daughter is going through this. I thought I was reading a post from my childhood. I had the same thing happen to me in high school. The "just because you have been in professional stuff don't expect..." and the voice teacher who said my voice was too strong and tried to change it to opera. He ruined my spirit and my self-esteem - and I never did get in any of the musicals except for one time in one song in "Grease" in high school. I got in a few plays, but only got the lead role when a new instructor and director took over, and she never did musicals. I had a horrible time in high school theatre, and people were horribly mean - and my parents were beside themselves. They tried talking to the director (I was horrified because that was the worst thing she could have done. Our director didn't go for parents upset about kids not getting a role.)
The only thing I can give you advice on, is to continue with the outside theatre world. In my opinion it's better anyhow - she won't learn as many bad habbits that need change in the long run. Stay in the theatre dept. in high school just for college purposes. But other than that, try to understand that it's not you...
I have that problem in college too. It took me 3 years to finally get IN a musical. (And now I'm at a new college cuz I am taking minimum credits...) but, I was told what the professors were saying by one of the musical directors. Basically he said that they were afraid to work with someone who had professional experience because they didn't have the same level experience. I was upset because my view was that I could learn from everyone and I just wanted to perform with my friends. Later those friends decided to call my agent/manager in NYC and some used my name and got in with her, all to eventually ruin their names and she kicked most of them out.
I know this probably isn't what you want to hear, but I can tell you I fully understand. If you want to email me you can... firstname.lastname@example.org
Things will get better - just tell your daughter to keep following her dreams, and not let anyone take her hope away. It's not her fault she has worked so hard and is talented. ;0) well, maybe it is lol. but in the end that is a good thing.