Why isn't my rabbit eating? :/?

I have 2 rabbits and they were separated just after I got them as they kept fighting. They are both coming up to 5 now. One of them is fine but the other one is eating nothing. She will only eat if you hand feed her at the moment, but even then she isn't eating anything really. She is still drinking, peeing and doing droppings but she cant seem to make it to her litter tray now and goes wherever which she has never done before. She is dangerously skinny now and I don't know what to do. I can't take her to the vet and my mum wont and says its too much money. Please help me. What's the best thing to do and what might be wrong with her?