My cat isn't acting like herself?

The non stop drinking and vomiting as well as the strange meowing are all signs that something isn't right. Call the vet and tell them all you have told us and tell them you want her rechecked. She might have eaten or drank something that is making her ill. The loss of balance is also a bad sign. Please don't wait to get her looked at and be very firm with your vet about finding the cause of all this.