Thanks for choosing Just Answer. My name Dr. Barbara, and I'd be happy to assist you today.
The fact that your girl likes to drink a lot of water may be the key to what is bothering her. This is actually a common symptom in our older dogs, and can be caused by several different disease processes.
These are sugar diabetes, Cushing's Disease, Addison's Disease, kidney disease, or a lower urinary tract disease. The way to determine what is going on for her is to have your vet do a thorough exam, collect blood for a complete blood profile, and collect some urine for a urinalysis.
Hopefully, this is helpful for you, but please get back to me with any specific questions or concerns of yours. . .