I mean... is it a website you can email and ask?
My guess would still be appendix.
They had her pegged as a regular QHx; but that's a guess as good as any of you guys' guesses. When I was riding her, her stride was extremely smooth compared to the quarter horses I've ridden, but not as smooth as a Thoroughbred.
I like the appendixX idea.. and it'd be awesome if she's a paso. XD You guys rock, thanks for trying to guess her breed.