I Cannot Quite Decide?

I think you should go with a western discipline. I think something with cattle might really interest her and keep her mind occupied. My mare is the same way as yours. She gets really bored with arena work, but she loves to work with cattle and trail ride. We manage to do a bit of western pleasure too, but we mainly focus on things that she likes to do. I bet your mare would look really flashy in a cutting pen or as a western pleasure horse or reiner.