My Cat Has Severe Diarrhea. She Has Been Dewormed, But I Don't Know What Else To Do For Her. She Is Getting Really Thin And Can Not Control Her Bowels. What Could Be Wrong?

First of all, control her diet. Stop giving her dairy products, because they can not digest lactose sugar present in them when they have Diarrhea. Don't give her food which contains dyes. They harm their digestive system. Give her cooked white rice. If she doesn't like it, try to give her mashed potatoes instead. Rice/potatoes could be mixed with boiled chicken or hamburger. Try to keep her hydrated, otherwise her life could be in danger.

What ever happened to your cat? I have a one year old cat and she is doing the
same thing...she's been back and forth to the vet. I had her spayed in March, I'm
beginning to think the vet that spayed her did something wrong.

You need to take her to a vet, I'm afraid. Imagine what would happen to you if you had diarrhoea and were left outside in the cold. You wouldn't last long, and neither will she. If she isn't trained to use a litter tray or you don't have one, you can't leave her outdoors - you must take her to an animal doctor/vet or she will die from dehydration and cold.