I can not express in words what I'm feeling.
I'm so sorry for you!
It's only a suggestion; what about have all your kitties cheked at the vet? Just to catch any illness in time.
what kind of medecines are given to you for her?
Even if it sound very weird can you buy or get some fresh blood, chiken blood, and fry it and try if she likes it.Blood is very good for the lack of red blood cells.Also iron (in a eatable form) which I imagine that you can find it at the chemist,at least you can here, is a med. for anemia.
We all know how much do you love your kitties.Best of luck. I will try to have some more information if you can give to me some more details. It happens that my father is a vet even if he's not specialized in pets,he best know "animal nutricion ", he must give me some advice or at least where to find information.