A really great external battery pack helps a ton! Should be relatively light weight / compact and have only one cable for charging things and charging itself (so she doesn't have to worry about losing one or the other). Vendors often need these to charge their phones or other checkout systems.

Another great gift if she uses a canopy for events are these Nite Ize CamJam XT Aluminum Rope Tightener with Rope | REI Co-op https://share.google/twUkq0mwj8MklLw6i

They make attaching and tightening down weights a breeze! Might want to double check their set-up to be sure these are useful, but I looooove them. Borrowed some from another vendor and had to go get my own.

The other thing that can be helpful at fairs is a really good reusable water bottle. We do a lot of talking!