All you can do for her at this point is treat her and follow vet directions for that to see if she recovers.
If the vet damaged her back you would first see if the vet offers anything and then if you wanted you could go to the group that oversees vet care to file a complaint about care quality.
If you are in the UK that group would be the RCVS
http://www.rcvs.org.uk/Templates/Internal.asp?NodeID=92575&int2ndParentNodeID=89737&int1stParentNodeID=89642
Hope this helps you!
I'd wait to see if there is improvement before deciding on euthanasia as I do like to give a pet every chance. You should know more at the check up point.
Legally you'd have to check with a UK lawyer and we do have a category for that sort of help here if you end up needing it.
But I'd start with the vet and asking what they are willing to do for you as you feel the injury was due to their handling. You won't know until you ask, and I find asking as nicely as possible, vs being angry even if you justifiably feel that way, can work best in such situations. You may be pleasantly surprised or you may need to go to the RCVS for help in dealing with the issue.
Pet Health Care, Rescue,Train,Breed
30+yrs pet vet care & nursing, rescue, behavior & training, responsible breeding, small animal care