Is she having appetite issues or being a picky eater? My old boy has cancer as well. I hope for better news with your girl! If she's not having any problems eating, then your plan outline looks great from the little bit I've learned! You want to limit the protein a bit as it feeds the cancer.
If she is not eating well, then it's basically a free for all. I went through at least 20 brands of cat food, both hard and soft, I tried tuna, turkey, hot dogs (don't ask!), chicken, baby food (was a huge hit for about a month) and I tried a chicken/rice homemade cat food, and a raw diet. He refused the raw completely, ate the other foods for a few days most for each before then refusing it. I finally learned that he was associated his nausea with the food. He would eat it one time or a few times until he got sick and then associated it with being sick, so I had to move into a different brand.
Appetite stimulants from the vet has helped, but again, only to the point until he would refuse to eat again. We tried an anti-nausea medication (sorry, can't remember it's name at the moment) and that has also helped. Once you can get the nausea under control, maintaining the same food is much easier.
For us, this medication was just temporary and he is now off it. My dog trainer suggested Purina Kitten Chow as it was the only thing her cat, who also has cancer, will eat. So out of desperation, I gave it a try and it has worked wonders. So I know it's horrible stuff to feed a cat, but it is literally the only thing he will eat right now. Even after being on the diet for a while, I have tried re-introducing in Felidae or Merricks or EVO or the homemade cat food and chicken, but he refuses them all and only eats his kitten chow. After a few weeks of a steady diet, we weaned him off the nausea medication and for now at least, he is doing great. I've gone through four bags of the kitten chow so far....unheard of for this cat! He's gained weight and is looking good. My only concern now that he's finally steadily eating is that he seems to be shedding way more than usual. So I need to do more research about additional nutrients for him I think. It's a sign he's still not getting all his nutrients. Or it could very well just be because no matter what I do, his body is sick and that is one of the physical symptoms, I'm just sure.
For us, weight maintenance is key as the cancer is a slow growth form in his cells and it starves the body of nutrients. The more nutrients I can keep in him and the more weight I can keep on him, the longer he will live. So I am in essence feeding the cancer, but for now, it's not wasting him, which is extremely important. If we can maintain weight, we can maintain a longer and better quality of life.
Anyway, so sorry about rambling about my situation! If your kitty is eating well, that's awesome and keep up what you're doing! If she's struggling, keep trying different things until you find what works for you. Good luck and I'll be wishing you warm thoughts while you await the test results!
ETA: I just read over your post again and it does sound like she is having weight issues. You might want to try mixing chicken gravy or meat gravy baby food with the dry cat food. For some reason, they seem to love it. My vet uses this for many of her sick kitty patients. It got me through a very tough month with Billy and helped him gain two desperately needed pounds in a short amount of time before the nausea set him off it finally. But it worked for a good month or so. I gave him a jar a day, half in the morning and the other half at night and he goggled it down faster than I've ever seen him eat anything else before. His favorite was Gerbers Stage 2 Chicken Gravy.
If she is a seafood kind of gal, try mixing some tuna juice in with the dry food for another option.
Chicken broth was another suggestion given to me, but didn't work as well in my particular case.
If I think of anything esle, I'll let you know! Good luck and Happy Holidays!