Fennel — Food safety facts
Safe to share · Cats · full breakdown on the linked food page
The bulb and fronds are safe in small amounts.
The full verdict, portion guidance and serving notes are collected on the Fennel food facts page.
Short answer
No, you don't need to worry. Fennel is safe for cats to eat, so a single exploratory bite from the bulb or fronds is not a cause for concern. It might give her a funny taste in her mouth or a bit of digestive curiosity, but it won't harm her. Just ensure she doesn't make a habit of nibbling on houseplants, as many others are toxic. If she seems perfectly fine afterward, which is very likely, you can simply carry on with your day. Always check with your vet if you're unsure about any plant she encounters.