I hear you and I feel for you. NOT a happy situation to be in. (have been there and will be there again!)

Suggestion 1.....Is there a room in your home that you can keep Cami by herself? Not having the stress of the other cats might be just what she needs. Also, "retraining" to the litter box always starts with confining to a small space.

#2.....have you tried Cat Attract litter?

#3.....Medicate Cami. There are several medicines to try for problem "pee-ers". It is the only thing that keeps me sane around here. I can't guarentee 100% success, but maybe pretty close. And maybe you'll have greater success.