@Valerie192 No personal experience, but I'd suggest covering any upholstered furniture with some washable covers, even if it's just some sheets, get an air purifier, you or your mom vacuum thoroughly on a regular basis, and then do a thorough deep cleaning on the room before having any guests. That's assuming the cat stays in her room, otherwise you'd have to do this anywhere the cat hangs out.
And if you have central heating, it might be a good time to get your ductwork cleaned. That might sound like overkill, but probably not for severe allergy sufferers.
Or you could change your listing desciption for awhile to say that there has been a cat on the premises, so that if a guest has cat allergies, not to book.