My advice is to talk to her before hand. Explain how everyone has to wait their turn. This does not mean that she will change her ways automatically. But it does give you the chance to talk to her while she is calm and explain to her what will happen if she has a fit and doesn't take turns. With our older two (our youngest is 13 months old. The others are 4 and almost 9.), my husband set the rule that if you have a fit about something (wanting a toy in the store, wanting to do a specific activity, etc.), then we have to say "No" even if we want to say yes. It has really helped a lot. If she were my child, I would explain to her that if she has a fit, we will have to leave the class and she will need to have a time out until she is calmed down. The important part of that, of course, is the follow through. It usually only takes a couple times of following through before they understand and start to get a better control of their emotions/tantrums. To follow, through, if it were me, I would probably tell the teacher that we need to leave the classroom/gym until your daughter has finished her fit and then take her to the car (or a waiting area) and sit her down and wait. The car is usually a good place to go. Put her in her carseat and close the door. Then wait quietly outside the car (to save your ears) until she is done. When she is done, tell her if she is ready to share and take turns, then the two of you will go back into the class. But make it clear that if she has another fit, you will leave (either to the car again or to the car and home).
My daughter (now almost 9) was the big tantrum thrower in our house. She spent a lot of time from 18 months to 3 years old in her bedroom learning to control her emotions and express them. When they start having fits, it is usually for 2 different reasons. 1. To get their own way. Or 2. Because they don't know how to deal with the emotions they are feeling (whether anger or sadness). In the second case especially they need a time out to learn to control their emotions. It usually doesn't matter what you say to them during a tantrum, they are too busy being loud to hear what you are saying. A time out usually allows them to calm down (sometimes it takes quite a while) and over time recognize and handle their own emotions. It is a learning curve.
We never ignored our daughter during a tantrum. We did however put her in a separate room so that we could remain calm and controlled and not say anything we didn't mean in anger. We would, however, be close by and check on her every couple of minutes and repeat what she needed to do to be done with her time out (stop having a fit and act like a normal person again -- we never said good or bad -- we didn't want her to feel she was bad because of the tantrums. She just needed to learn to control her emotions and express them in a more healthy manner.)
Anyhow, I've rambled on quite a bit. (And by the way, I learned how to deal with them from my Mom. I am guilty of being a tantrum thrower in my toddlerhood.) I hope my email helps a bit. Please feel free to ignore me completely if you think something else will work better. You know your child and only you can really decide what will work for you. Good luck.