I think she's definitely a cross. She seems to have no defining breed characteristics that jump out at you. I would guess she probably has some QH in her since it's such a popular breed. Is she gaited? Do you know anything about her sire or dam?
I would say QH because of her build (stocky and nice rounded hindquarters) and TWH because of her higher set neck and she has that head type (wider set eyes and full cheeks) that I have only ever seen on TWHs, plus the fact that you say she is gaited.
I could be way off, but that is still my guess! Curious to see what others think...
She reminds me a little of my reg. QH Palomino mare Miss D.Eva/Skip Sparklin Dotty! I love palominos too.