Young cat just had kittens, now acting funny?

My friends 8 month old cat recently had kittens. Ever since she gave birth to the kittens she's been acting very strange. She wouldn't eat, her coat was losing color, and she had trouble walking. After noticing this, we took the kittens away because I figured the kittens were sucking all the life out of her. I also searched the internet to find out if there were any possible diseases she could have, and the first thing I looked up was leukemia. She had quite a few of those symptoms. However, ever since we've been caring for the kittens, she's been eating and her coats gotten color and she's walking better, still wobbly as if there's something wrong with her back legs, but better. Do you think leukemia is the culprit, or simply having kittens so young put a toll on her? any thoughts and advice would be GREAT!!! thanks :)