Along with what Susan wrote, what are you feeding her? How green is she? What's your reaction to her when she gets worked up?
Do you have a coach or someone experienced that can evaluate (on the ground) what is exciting her? If you don’t have a lot of experience riding, you could be missing a pain issue. Or it could be a rider/training issue that can be resolved.
Without knowing what she actually does, it’s hard to pin point if it’s pain or training tbh. That’s why having someone help you through this is the best option.
Physically. She gets excited and won’t calm down
Sorry if this is a silly question, but do you mean hot as in temperament wise, or hot as in physical temperature?
If it's the latter, does he/she sweat relative to their heat?