Hi there, vet Andrew here. I see you're offline so I'll leave this as a message for you.
This may not be an easy one to answer, so I'll have to make a few assumptions, such as that you've had her for a long time and so know her dietary history and that she's been looked after well in the past.
It sounds like she is having some back leg weakness or pain, which could be the result of an injury such as a fall or being stepped on that you may not know about. Tortoises' feet do indeed grip better on tiled floors, so of course try to keep her on these surfaces rather than on carpet. You have been doing the right thing by picking her up when she has difficulties, as this allows her to move and so 'free' her legs. The fact that she is able to move at all suggests that her skeleton is stable and so you have the option of keeping an eye on things and hoping she improves, but I would not recommend this as there further possibilities:
When a bird or reptile starts to have difficulty moving I am always concerned about gout, which is an accumulation of crystals in the joints. The treatment is easy, just a drug in her food but needs to be started ASAP. This can be diagnosed by X-ray and a blood test. The X-ray would also help rule out any fractures, so for this reason I would recommend taking her to the vet and dicussing the issues above.
Lastly, it's also possible that she has a viral disease which is affecting the nerves to her hind legs, which will need careful monitoring, nursing and hygienic precautions to ensure it's not transferred to any other reptiles.
I hope this helps. Vet Andrew
Thank you Andrew. This was very helpful.