Daughter and husband want a cat but I do not

My husband and I just got temporary custody (will last anywhere between 1 to 2 years) of his daughter about 4 months ago and she really really wants a cat. The problem is, we have a dog who is not cat friendly, she has killed cats in the past. And even if we could make it work, I am 100% positive my step daughter will not clean out the cat box often enough and I will not live in a house that smells like cat pee and poop. And what if the cat ends up being a bad cat that pees on the walls and baseboards, or God forbid, her bed. Id much rather get her a dog but she doesn't want a dog, she's a cat person only. There's been mention of possibly getting her something else, like a ferret, but that also raises the concern- what if it slips under the door and she witnesses a traumatic scene when my dog gets a hold of it. My husband says we really need to get her a companion because she was ripped away from her mom and the rest of her family and friends to live in a different state (not our doing), her cat just passed away before she came to live with us, and then recently, her new best friend just moved a hour away. So I do feel for her but I don't know what to do for her. Any advice or solutions?