I think this might be to do with her spine (disc problem). When a disc blows, it's very painful. However, you won't find an accurate diagnosis on here - you need to be able to get to your vet.
Do you have another relative or even a close neighbour who, despite the late hour, could get you veterinary help? Otherwise you'll just have to keep her as immobile as possible, until you can get her properly assessed.
We can only guess and although she's not old-old for the breed, anything might have happened to cause this - don't pull her around any more.
Add - There is NO NEED to hit the TD button on my answer - I, like everybody else on here, can only offer their own thoughts - guesses, as said. The TD button is not for anything else - only usually for something that is DEFINITELY INCORRECT. Note I've used the word 'might'.