I am sorry I have no personal experience with hip displaysia itself but I have experienced many other joint, muscle, ligament, etc.. problems.
She could have something as major as displaysia but it could be something as simple as anal gland problems. I am sure your vet will be of more help. I would also contact the rescue organization (IF I remember correctly that's where you got her???), they may have more information on her health that they didn't share with you for one reason or another and they actually *may* help you with some of the vet fees.
I wish yous the best of luck at the vets. Please keep us posted. {{hugs}} to you all!
Sue