Has she recently started drinking out of the sink? And her increase has been since getting used to that? I ask because my old kitty at my dads, and my mom's cat both love water from the sink. Typically the bathroom. So they run to the bathroom every time. For them its a combination of fun and attention. I think in some ways they become *trained* that when the humans go into the bathroom, its time to get get some water.

You should probably take her to have a good exam from the vet before assuming its not health related of course. I hope its just something she really enjoys.