Let her have as much food as she wants, for now - cat milk is basically junk food but its quite good for calories so maybe a bit of that to help her bulk up? I'd make sure she's on a really high quality food with all the vits & mins she needs to get her condition back, too - perhaps applaws, nature's menu or similar. I'd not worry too much about putting stuff in her coat, she'll take care of that soon enough once she's got the good stuff on the inside to grow lovely lush new fur.