Generally, if you're certifying a dog through the Orthopedic Foundation for Animals (OFA) they won't do a 'final' until the dog is 2 years of age. Prior to 2, they'll give you a preliminary evaluation, but it isn't "official" until done again after age 2.
However, you can get your dog evaluated even if it's not a purebred. All it takes is an xray and an experienced orthopedic vet...I'm not sure, but I suspect that OFA will evaluate an xray for you for the same price as they'd evaluate one for certification. It's pretty reasonable (last time we did it I think it was US$35 for a hip evaluation...above and beyond what your regular vet charges to take the xrays, of course) if you want to go that route.
If you don't want to use OFA, any experienced orthopedic vet would be able to help you out.
The extra stretching almost sounds like she's working a kink out of a muscle--so maybe she just has a soft-tissue injury