You could try Rescue Remedy for pets. It's an all-natural bach flower essence that you can put in her water, on her skin or in some food. I did that with one of my cats who peed in our house. She peed all over our rug so the Rescue Remedy was my last resort. As long as I gave it to her daily, she didn't pee on anything. I also gave it to another one of my cats when she got depressed when one of our cats died. She was biting off all the hair on her legs! The Rescue Remedy calmed her down. You can buy Rescue Remedy online or in a health food store. It's not expensive, and it can't harm your cat. They carry it at Fruitful Yield, if you have one in your area. There's one in Schaumburg and one in South Elgin.
I would try Cat Attract litter. I don't think it's a litter box problem, but that worked for us. It's just the right size and the smell attracts the cats.
Have you looked into a raw diet for your cat? Will she eat raw, organic chicken? I have heard of cats whose health has been turned completely around by going on a raw diet. You'll have to research it, my one cat won't eat anything but dry cat food. Cats' digestive systems weren't made for dry food or even our version of wet food.
My cats also drink alkaline water. It has made their fur shiny and so soft. Our vet said they are in excellent health! They are also not too fat. I attribute it to the alkaline water. In fact, when they don't have alkaline water, just regular water, in their bowl my one cat meows and "yells" at me, running back and forth between her bowl and me.
I also agree that if you can give Kitty a room all her own, maybe the garage or one without carpet, she may calm down and live a happier life. If you have a holistic vet in your area I'd recommend that. They probably could solve your problem better than a regular one.
Good luck! You are a responsible pet owner!