When she tries to speed up I would ask her to slow down with rein pressure and be calm. When she gives and slows down to the speed you want give her back her head, keep doing that until she gets it. I have a super spicy Appaloosa mare too

Some mares have serious issues with performance when cycling and some you’ll never notice. My mare can show and act like a lady in heat. My familhs rodeo mare is certifiably insane when she comes in to heat. To the point she’s dangerous to ride. We consulted with a veterinarian on her health and she had a full exam as if we intended to breed her. Her physical health checked out. Ultimately we tried managing it through training and it became a don’t ride her inheat situation. Because of our area and the seasonally polyesters nature of horses not using her when she was cycling was not an option. She ended up going on hormones to prevent heat entirely. It’s a pain from a management standpoint as you have to give her a shot weekly but allows her to perform and use her talents safely. Before this she was putting her rider and herself at serious risk. She doesn’t stay on it year round just during the rodeo season. Might be worth talking to a veterinarian for a consult on her. Or mentioning to the instructor.

Works some times with rein pressure and leaning back, but other times she'd fight and yank her head, almost tipping me a few times.

I've had a talk with the instructor about this, he is a new instructor this year, and his teaching methods are very different from the other instructors so the horses are not used to it (he is using us students to teach the horses while he teaches us).

I'm talk about warming up the canter with heads immediately high and reins ultra short as though jumping. The horses naturally want to lower their heads but we should 'resist it' and not be afraid to pull and feel the weight of the mouth. The horses don't like it (me neither), but they need to learn, but that's also why she's speeding up/ yanking me forward in hopes I let go.

I feel like the more I ride the less I understand how to ride hahaha....

This is super insightful!! I've brought this up too, and they say from a school's standpoint they do not have the budget nor the manpower However they've agreed to further monitor the situation, and during riding classes if she acts up, to immediately lower the jumps and give her much more space. They can't not use her for classes as there aren't enough horses to go around, but they'll limit her to intermediate-advance students only as a safety precaution.