As far as we know, and the vet has checked her thoroughly, she has no hip problems. She is very fast when she makes up her mind to run. I think she is a bit lazy and dependent on her mom probably. I may try to make her a low obstacle course I can take her through on the leash to see if she can jump over low things first. I'll have to lure her with a treat, but that usually works. The step might be a great idea for the car though.
Thanks everyone. Keep those great ideas coming.