"What can I do?" You need to get this girl to a Vet for a checkup.....You don't say how old this dog is or how long the symptoms have been going on....We on the forum can only guess as to what the problem may be......Any dog that can't or won't move, is ill....I agree w/Margot, this behavior is probably pain related, but you need to find out where the pain is coming from....
Get her to a Vet ASAP to have her evaluated & treated....The sooner, the better!
Keep her hydrated till you can get her to a doctor.....Dehydration is dangerous, just by itself....Good luck and let us know what happens....I hope she feels better, soon.....Karla
Hard to tell what may be going on. My first suspect would be pain somewhere.