I didn't know why she behaved this way and neither did the vet (surprising answer below)
After completing this video, we learned what's the medical problem Snowbird is suffering from that causes the weakness in her hind legs. The source of the problem is actually in her HEART and her condition is called: Cardiac Shunt.
Later on today the cardiologist will determine if we can fix this with surgery or by managing this condition with medication. Please keep your fingers crossed for her, and if you can, please get your own Lucky Leash today and ALL the funds will go towards her medical care: https://www.HopeForPaws.org
If you would like to adopt Snowbird, please contact our friends at ART N' Paws: http://www.ARTnPawsAnimalRescue.org - they have been so amazing in working with the neurologist and cardiologist.
Hope For Paws will of course pay for all of her medical care and I just wanted to thank you all for your support.