I personally think the Innova Evo is a really good food, and have never even heard of Natural Balance. But you're right, at this point, the important thing is just to get anything into her, so I'd feed her which-ever she likes the best!
I'm SO glad you got that second opinion from a better vet! Sounds like you are on the right track, and that you have a good vet to work with now. Phaewryn VT low cost Spay&Neuter, and Emergency Financial Assistance for cat owners: http://ucat.us/VermontLowCost.html Special Needs Cat Resources: http://ucat.us/domesticcatlinks.html