What type of dressage saddle should I buy?

I am in search of a dressage saddle for my new horse since my old saddle does not fit her, She has a medium wide gullet, she is around 15.2hh and weighs about 827 lbs. She is a thoroughbred type appaloosa. I am 5'1" with a long femur and usually ride in a 16- 16.5" saddle.