Celexa is used to treat depression. A common side effect is anxiety. It wouldn't be the first choice of drug to adminster to someone already suffering from anxiety.
Vistaril is anti-anxiety. Prozac is an antidepressant - BUT, you need to take her comment that she would rather die seriously. Suicide can be a concern on Prozac.
Find another doctor, a phychiatrist. They are a medical doctor and are able to prescribe drugs for the treatment of anxiety.
I wouldn't recommend a counselor or psychiatrist, not from what you're describing.
Also, notify the school that you will not tolerate any form of bullying, even by the teacher. Threaten them with a lawsuit. You have rights, the school works for YOU and YOUR DAUGHTER not the other way around. Change teachers or schools if you have to.
I agree with medic-dan. Find a really good phychiatrist or social worker. Have them try CBT first before drugs. They will get to the bottom of why this starting happening to your daughter? Maybe she is fearing that school will be ending and college will be beginning? Try to get her back to normal w/o drugs. Those are really nasty and cause some bad side affects. then trying to get off of them is not fun as well. I think too many doctors are to quick to write up prescriptions for people that really can get over their issues with speaking to a trained professional in this area. Really check CBT first. If the drugs are needed then combined with CBT will give her a greater chance of staying good when the drugs are weaned off. Good luck show as much love as you can as they are young and need it.