my girl friend used to give me a hard time about how much time I spend on my tank, I took her to the LFS and let her pick out any fish she wanted. To my surprise she spent 2hrs trying to find the "perfect" fish. Now she has an little interest in the tank (helps feed, keeps an eye out for problems) and is a little more understanding of vested interest and committment required to keep these tanks running healthy.
So maybe try to switcheroo, trick her into going the LFS and picking something out, maybe set up a nano for her?
Cheers,
Josh