>She has always been like this
I have one that is a very visible drinker - he drinks long, loud, and messily, leaving trails of water from bowl to ...well as far as he can get!
The other is more discreet, much quieter, and much cleaner. He also drinks much less, even taking their different weights into consideration.
Both prefer our home water to anyone elses and drink noticably less when we are away. Awkward little toads :) I'd say if your girl has always been like this then it's probably nothing to worry about. A change in drinking habits would be of more concern.