By the way, if she is just lethargic, and doesn't feel like moving (as opposed to CAN'T move) -then there has to be a cause for that.
The cause could be anything from just feeling a little unwell...to being very tired, to actual pain either in her legs or elsewhere.
If this is the case (you feel she's lethargic suddenly) then perhaps a visit to the vet would be in order anyway, to find out the cause.
When you say she doesn't want to get up and walk, do you mean she can't? If you believe this is a situation where your dog suddenly CANNOT use her legs, then this is serious. Something has happened to her, presumably something has happened to her spine. If that's the case, and she simply CANNOT walk or move, then you must get her to a vet as soon as you possibly can.
The best way would be to slide a large board under her, and get someone to help carry this to the car, and then to the vet (if your vet isn't the sort you can call out for a home visit)
Also, when you say there have been no other symptoms, do you mean she has tolieted perfectly ok, eaten ok,? I'm not sure I quite understand that, if it isn't possible for her to move..?
Does she still have control of her bladder and bowels?
I am not exactly clear whether you mean she is simply lethargic, and doesn't WISH to move...or whether she cannot move at all.
I may be jumping the gun here, but if by chance there is paralysis, (depending onmany factors, including what the vet says after tests are done)...it may not have to be the end for her. If she is a suitable candidate for a walking aid, there are quite a few companies you could contact to design her one. They do not cost the earth, and give paralyzed dogs a new lease of life.