No kids at wedding

You could give her a stuffed animal - I saw a shop on Etsy that sells an elephant with her name embroidered on its ear. Or, you could also include a couple books and a snack. If you're looking for things to gift her that would also keep her entertained during the wedding, I would probably avoid anything that makes noise or toys such as a ball (or anything that is intended to be thrown around).

Coloring books would be great. I typically give children necessities such as clothes instead of toys. When I do buy toys, I try to make sure they are educational ones.

For our wedding, we only had my husband's two nieces (our flower girls) that were 5 and 8 at the time and his nephew (our ring bearer) who was 3 at the time. I have linked the items below that we gave them. In addition to those items, I gave his nieces robes similar to the bridesmaids, but in a floral pattern rather than a solid color like the bridesmaids.

https://www.etsy.com/listing/641597617/baby-boys-personalized-dinosaur-plush?ref=yr_purchases - I picked a dinosaur because he absolutely loves dinosaurs. I'm sure you could get a cute stuffed animal that your niece might like.

https://www.etsy.com/listing/616967438/personalized-flower-girl-gift-flower?ref=yr_purchases - They loved the pillows. We just saw the girls a few months ago and both girls had to show me that they still had their pillows.

Snacks and games would also work. Or even kid jewelry

Maybe give her a barbie

Bubbles, a reading book, colorful bracelets. One of our ring bearers fell asleep ❤️ so maybe a little pillow 🥰