I would get her to a specialist (board certified orthopedic surgeon is best) as soon as possible. It is very probable that she has torn the ligament in that one leg. When they have luxating patellas they are at risk of tearing the cruciate ligament. Here are some links to explain the two:
Yorkie Haven Rescue - Cranial Cruciate Ligament Tear Info Yorkie Haven Rescue - Patellar Luxation Info
Dogs do a very good job of hiding pain. Just because she is not whimpering or crying does not mean she is pain free. If she has a torn ligament, that is painful.
If you don't know of a specialist, here is a link to find one:
ACVS - Find a Surgeon in Your Area
Good luck and keep us posted, please.