Originally posted by boscibo
If she doesn't stop by, I would call her and ask if she is absolutely, positively sure that it is her cat Merle because you have been getting other calls and want to make sure the cat is with her rightful owners. If it isn't really her cat, or she has doubts, she might be willing to give her back to you. Then you could screen the other callers and make sure they aren't the real owners.
I think you should call around in person and say that....
'You are here for the cat, this cat is not hers as you have an owner with photo proving that Splice is their cat (Call her bluff)'

Watch her reaction carefully. See if she can generate any good proof for you.

Legally a found cat/kitten with no ID or microchip IS a stray.

I would return the cat if the 'owner' had proof of purchase or adoption or vet records or photo dated prior to you finding the cat.

But if she is going to lie to get a cat, that means she is not willing to pay for a cat. If she won't/can't pay for a cat, how will she treat it. What happens if Splice needs medical attention.

I'm sorry but I am hearing warning bells, I would get this cat back and rehome/keep to a better person who doesn't lie.

PS. If you used ffrontline does not wash off in the rain, it is placed on and absorbed though the skin after 5 minutes the treatment is complete, though the cat has a sticky patch for a day or two but that is better than fleas.