That could be a lot of things, but if she's that weak or unable to move her lower body you need to go to a vet ASAP. Can she wrap around your arm when you pick her up, or is the lower end just not working right no matter what the situation?

Also, if you're worried about Body Inclusion Disease, I'd strongly suggest going full on quarantine until you can rule it out. Separate room, separate equipment, all that. I don't have personal experience with that disease but it's something I'd want to take the absolute highest level of caution with.