I found a wild baby bunny, what do I do?

My cat caught a baby bunny. She killed the first one, and I found her while she was toying with the second. She (I don't know if it is a she but I'll say it's a she for now) has one leg that is completely limp, and another that seems out of place. These are both her front legs. I KNOW we need to take it to a vet, but my mom won't because she doesn't have the money. We wrapped it in a towel and put her in a padded shoe box with the lid on (with slits in it) so that she is in a dark area. She is very little, like fit in the palm of your hand little. She is very reactive and tries to move. One of her eyes won't blink either. Is this all we can do for her according to the situation?