No, no, no...sorry to be emphatic, but if A takes the cat, she will have committed theft. The cat is another's property and A has no right to it.Unless there was some agreement that A will care for the cat--e.g. food, litter, medical care--A is under no legal obligation to do so, and if she choose to spend money and time on the cat, that is essentially a gift to the cat's owner; doing so does not give her any right to the cat. So, for example, A does not have to pay for a C-section, and if she does, that's her voluntary choice to spend the money on someone else' behalf. A could let either C or D pay for the medical care, or let the cat suffer the consequences; she may not want to do that, but again, that's her choice and does not give her any rights.If there was an agreement to provide cat care, A may sue for any money owed her under it (e.g. for reimbursement or as wages), but that still doesn't give her the cat.