Hi there and thanks for your question.
I get very concerned when an older dog starts to drink and urinate a lot. There are a few things that can cause these symptoms.
In an older dog we worry about kidney disease. This can be due to toxin ingestion or a virus called leptospirosis but is often simply due to aging changes in the kidneys.
Diabetes can cause these symptoms as well.
If you girl is not spayed, an infection in the uterus can cause this and is very serious.
There is also a condition called Cushing's Disease that can cause an increase in thirst and urination. This usually also causes an increase in appetite, but as the disease progresses it can cause other sicknesses that reduce the appetite.
You can read more about Cushing's here:
Be sure to follow the links on the right hand side of the page as well!
It does sound like she should see a vet and have some blood and/or urine tests done.
I hope she is ok!
I hope this information helps! If you have more questions regarding this problem, just hit reply. If I am online I will respond right away. Otherwise I will respond as soon as I come online again. Or, if my answer is sufficient, then please hit accept. Thanks!
The above is given for information only. Although I am a licensed veterinarian, I cannot legally prescribe medicines or diagnose your pet's condition without performing a physical exam. If you have concerns about your pet I would highly advise contacting your regular veterinarian.