You say she has regular checkups. Have you mentioned it to the vet at all?

I don't think I would be particularly worried about it in isolation. I know that drinking much more than usual can be an indication of kidney problems, but you only mention eating. If you are concerned, I am sure you could phone your vet and just ask them what they think.

We used to say that our Samantha lived on fresh air, because we almost never saw her eat, whereas the other two ate all they could. I think some cats are just different. We have had our cats for 9 years now and although we occasionaly see Sam eat now, the pattern is not really much different.