I'd honestly be more worried that her loss of appetite and her drinking a lot of water might mean she's got some other health issue. If her eating doesn't improve soon, I'd take her to the vet for blood and urine tests.
On the other hand, loss of appetite can actually be a symptom of hairballs. That combined with her coughing might indicate she's got a big hairball that she can't get up. You can buy a hairball remedy at your local pet store that helps move the hairballs along. It's a thick pasty substance that works best when given through a syringe (don't know if I spelled that right). It's not always easy to get the cat to swallow the stuff, but it works very well. I could never get my cats to just eat it on their own. I always had to sort of force feed it with the syringe. It helps to have someone else hold the cat still while you administer the gunk.
You can also buy hairball treats that might work faster than the hairball food does. My cat loves the treats, so I give her a couple every few days to try to help with the hairballs. (You'd probably have to give them every day until the hairball comes out). I also brush my cats a lot more this time of year. It really helps keep the fur balls down.
Good Luck. I hope the problem is just a hairball and that she coughs it up soon!
Shelbygirl
