That led her to suspect that there might be a problem with that tomato, so she picked it and sliced it open, to find that her suspicions were confirmed: a Tomato Pinworm, Keiferia lycopersicella.
The larva of the bug usually enters the tomato through the calyx, which can make it difficult to detect unless you see the frass (aka bug poop), but this one had entered on the skin of the fruit which made its entry point much more obvious.
In fact, in the picture below you can still see the entry hole above the sliced out portion of the tomato.
Tomato Pinworm |