Are you feeding her kibble or canned food? Kibble is naturally dehydrating. I know of several Maltese who have had elevated kidney values with high protein kibble (Acana and Evo). I personally would not feed a high protein kibble to a breed like Yorkies or Maltese who are prone to liver disease.
Protein is processed in the liver and any waste materials are filtered and excreted by the kidneys. High quality protein does not generate large amounts of waste that needs to be removed from the body, but poor quality protein which is difficult to digest does and thus puts stress on the kidneys. The liver needs water to process protein and as a medium to carry waste products to the kidneys, where they are filtered out and most of the water is reabsorbed. The less concentrated the waste products in this primary filtrate are, the easier it is for the kidneys to do their filtering work - that's why it is unhealthy to feed dry food only and so critical that dogs eating mostly or exclusively dry food and dogs with liver disease get lots of extra water. Dogs who eat mostly canned food or a home prepared diet automatically take in more moisture and do not need to compensate as much by drinking.
The Dog Food Project - Is too much protein harmful? A Kibble Fed Dog is a Dehydrated Dog and That’s Bad!