You say the cat has been doing this for two years. In not finding an immediate solution you reinforced the behavior, then get mad at the cat who is being a cat.

The litter box would be my guess for the initial issue. Perfumes in the litter, its location and cleanliness. After the period of time that has passed it may be hard to break the habit.

Move the litter box, change the type of litter you're using, reintroduce the cat to the box. She may need more than one box. My mother's cat has two, one for each function, and it has to have a rug under it. He's very weird that way. Your cat may need a box closer to where she hangs out.

They are little people, which is why so many humans hate them.

Use a spray bottle with water in it when she's bad and a loud, "No." They don't like water in the face.

But, I keep coming right back around to that litter box.