My brother had a yellow lab named Bailey. His lab had hip dysplasia. Unfortunately, Bailey bunny hopped like that as a pup. If your pup is favoring a hind leg by putting weight on her two back paws at the same time, that could be an indication there is a problem with her hips. I would recommend that you get an initial examination from a veterinarian to determine for sure whether or not your pup has early stages of hip dysplasia. You need to address this issue ASAP. Good luck. Sending good thoughts your way. I hope I am way off base.
Here is a good video by Dr. Anthony Cambridge on the subject:
https://www.youtube.com/watch?v=SHCIT87jY0M