If she IS wild and you can't keep her due to permit laws and all that, PLEASE call a wildlife rehabber asap! They can get her on what she needs and prep her for release when she's old enough, as well as usually pairing them with any various mother ducks they get in and they don't charge for taking in animals. Cat food and bread is definitely not a good diet full-time for a duck, and while I haven't personally dealt with the issue, I can't imagine drinking and bathing in chlorine is good for them - especially such a young one. She's definitely a cute duck and it's very kind of you to try to help, but the Migratory Bird Treaty Act does make it illegal to take birds out of the wild unless they're unsuited for return. Just hoping to keep you and your wallet safe, as well as get the bird healthy. Was it near a pond when you found her?