In my experience, It's her way of saying "Spend more time with me". Had this isue and still have it from time to time.
What I did is I started a Nano and cycled it, grabbed her arm and off to the Local fish shop. Told her she could have any Betta she liked. (She loves Betta's) So there I found her weak spot.
The other day we where discussing a potential move and I started rambling about a Fishroom as the potential home has one more bedroom. There and then she responded "Nuh Uh!" What will the guests be looking at when they visit.
Problem solved. Get her involved, even though she is into Marine Biology she will still have a soft spot for that one fish or certain look that will make her smile.
But I still get the odd eyebrow move when I fiddle with the tanks every night.