Please don't be upset with your kitty. I think that a cat's instinct is to bury their poop. You still need to keep your kitty confined until you discover what is wrong. I am not an expert about this but I do know that many sites have advice about this problem.
Here are a few ideas that you may not have tried. Make sure that her food & water are not near her litter area. Do you clean the areas were your kitty has pooped so that no scent is left? Have you checked out the bottom of your kitties paws for possible cuts that may hurt when she steps into the litter. Use a no scent litter for sure. I would have a radio play soft music in the area where your kitty is confined, so that she is not stressed by noise in your home. Remember....your kitty can feel your stress. That may be adding to the problem. I wish I could offer more help but there is a solution...keep looking until you find it. I'm sure that other members will have some good ideas for you.