When you move the leg back to stand below the buttock, I imagine it wouldn't be sickle hocked at all. "Sore shins" is very vague however and should definitely be looked at by anyone considering her. As for the stance - she's a broodmare, so it could be a pelvic tilt, or just a weird shot. (Either way, people breed poorly conformed horses all the time, so there's not much we can say either way unfortunately.)
"The art of riding is hard to find and easily lost."