Oh gosh, what a dilemna. I feel for you. I have 3 indoor cats, 1 of them almost 16. She is having lots of problems now (health issues) which I have to constantly clean up. Its not fun. I deal with it by laying paper towels on the floor under the boxes, use the plastic box liners and then lay kleenexes draped over the sides of the boxes. That way I can just pick up the kleenex that is soaked with pee or poop. She can't seem to get it to go IN the box. I love my animals dearly, but I gotta admit...they just are NOT meant to live inside houses. Best of luck to you with your sweet girl.