Karen, I'm so sorry to hear your news but as others have said, don't let the vet rush you into a decision. Personally, I think the fact she is feeling pain is a good thing......if she wasn't feeling anything, I would be more worried. She could possibly have bruising of the spine which would cause her not to use her legs. I'm sending positive thoughts but don't give up hope, give her a few days and hopefully the use will come back. If in doubt, get a second opinion but from what you've said, I deffo wouldn't allow them to pts, her body needs to recover from the trauma and then another assessment done.
Take care hun, and thinking of you, xxxxxxxxxxxx