I had the same concern with my pup when that leap off the tall bed seemed rather high for her. However, I was more concerned about her front legs as those limbs seemed to take most of the impact.
I remember I was concerned enough to get my pup ( with my assistance ) to slowly slide off the bed while on her belly so the drop was less. I kind of laugh at myself now but at the time I felt it was a real concern regarding the integrity of her joints.
I think paying attention and minimizing any undue shock to a puppy's joints is probably a great idea. But, as you stated "she suddenly jumped off", it takes a lot of vigilance to stay on top of a GSD pup and their self education.
Hoping she is just fine !