I think she's got potential. Sickle hocked refers to the back legs being set too far under her, and I'm confident that it is just a result of her not being set up right, and not too happy about being in the clipping frame. I think she's sound enough that it wont be a problem once she's a bit happier on the halter.
She does have a lot of air under her but
she looks very full french, or close to it, and that is normal for her type. With time she will deepen and balance out but in the meantime, you are probably going to be placed down for less capacity.
She's a sweet heifer - feminine, long, with adequate structure. You should be very proud of her
Have fun with her and keep us updated as to how she goes at the show