My cat seems quite disciplined since coming of age and quite easily uses the litter. My problem however used to be how to deal with the furs she and the dog left on my rug until I read a review by GearTronics recommending some domestic robots that does the business of cleaning the house for me...
Perhaps your cat needs reassurance. The presence of the new cat must have triggered some level of envy and made it wonder if the other cat's behavior had made her enjoy more attention.
They are some litter boxes here for those who would need one for themselves.
Cats sometimes nibble on a few blades of grass in your yard and almost immediately afterward you’ve probably seen her throw that grass right back up. It might seem odd that kitty would enjoy eating something that obviously makes her sick, but there are a few theories that seem to indicate grass...