My Bobo had large, long ears too, and a long nose to go with them. I always told him he was adopted because he didn't fit in with all my other pug nosed, round eared others!
She has used the box a few times, on her own, so she knows what is that for... Only that sometimes she forgets it.She might not be used to a litter box. Maybe just keep setting her in there until she realizes what it is for?
It might be. Should I give her a tray with a lower rim?You said she was a little wobbly. Perhaps stepping into the box throws her off and she's afraid she'll fall over.
I thought the same, she might be a little confused by the disease or what she's been through.I'm just wondering maybe if she does have a tumor it's pressing into her brain and making her a bit confused. What about confining her to a room or a bathroom? I know that's not the nicest thing but it's not sanitary for her to use your floor like a bathroom either.