Eh, she’s cute, she’s young, she’s all ramped up in a wee spot–many a horse will bounce and prop in that situation.
My (otherwise lovely and nice moving) driving pony has been known to impersonate a pogo stick when turned out in a round pen, which is apparently more exciting than the large field he actually lives in… the hoofbeats in the night are probably not a zebra, the little mare is probably not abnormal, and it sounds like she’s about to land on her feet regardless.
Regardless of discipline or competitive goals, dressage training (be supple, be forward, use your body effectively) is helpful.
Plan to enjoy the creature. Don’t borrow trouble, especially not from the interwebs. Best of luck and open roads to you and all the mustangs.