Even if they need protein, they still need a PLANT based protein. Just like you wouldn't feed a growing puppy a diet consisting of nuts to get their protein, you shouldn't feed an herbivore a meat based protein source.
As I said she needs to see a competent vet because she's got some serious health issues going on and the vet you're taking her to doesn't seem to even realize what a correct diet is. Tooth problems due to malnutrition and lack of fiber are probably very likely at this point, but the longer she goes without treatment the more dire it becomes.
We are as gods to the beasts of the fields. We order the time o' their birth and the time o' their death. Between times, we ha' a duty. - Terry Pratchett.
"Men have forgotten this truth", said the fox, "But you must not forget it. You become responsible, forever, for what you have tamed. - Antoine de Saint-Exupéry