Can you keep a pet you take care of if the owner won't pay for food or vet bills?

Question Details:

My friend A is house sitting for our friend D's mom, C, with D there as well. C has a cat that she left there for D to take care of, but A ends up doing all the work. Besides buying cat food and litter, she has to feed her, water her, and clean the litter box. Now the cat is pregnant and may need a c-section. A is going to have to pay the bill. Legally, can A keep the cat when she moves out? (will be soon because A and D aren't getting along). Important Notice