Hi and thanks for posting. I've had a lot of success with isolating a cat when they were eliminating inappropriately, so your idea is a good one to try. Try different substrate material as litter, such as shredded newspaper, or regular clay if you are using the scoopable kind for a while. Sometimes they don't like the actual litter material. Keep it real clean and fresh at all times.
But the first thing I would do if I were you is to have your vet do a thorough examination with lab work to rule out possible urinary tract infections or parasites, both of which could cause this type of behavior, as well as a lot of other health-related issues that may be contributing.
What is your kitty's name? How old is your cat, and do you know anything of her history? How long have you had her? What kind of food do you feed her? (Just being nosey *smile*)
As an aside, did your Mom give you permission to have this cat, or did you just sort of bring her home and let her sell herself? *smile* Either way, you would be a very responsible person if you reminded your mother (gently, please - do this VERY gently!!) that a pet is a lifetime committment, and that you are prepared to accept whatever consequences being a pet care giver may bring your way - including having to clean up after them when you have to. It would be totally irresponsible to even think of getting rid of this kitty without at least trying everything you can to correct the problem. If your mother gave her permission for the cat to live with you, then she allowed you to make that committment and she should allow you to follow it through, no matter what may come IMO.
Please come back and let us know how things go - I am going to worry about you & your kitty until I hear from you again.
Take care and best of luck,