Cat is in litter box constantly. Help!?

If she's a baby, she's probably playing around in there. However, the strong ammonia odor could be a sign of an issue. She may have a urinary tract infection, or a pH imbalance that causes crystals or stones. If she has a urinary issue already, the urinary health food could actually be making it worse, since it starts off assuming your cat has a normal urine pH. She may also not be drinking enough, causing her urine to be concentrated. I would get her to a vet and send in a urinalysis to rule out any issues. If she comes out healthy,she's probably just having a little party in the box because she thinks it's fun.