Sharing photos on Mac via thumb drive to another PC

If she has a Mac, with /Applications/Utilities/Disk Utility.app format the thumb drive as APFS (select View > Show All Devices and Erase the topmost device: select GUID partition scheme first, if APFS is not readily displayed). Then in Photos > File > Export > Originals (or edited versions as .jpeg if you have done any edits you want to send as well).

If she has Windows/Linux (works also for a Mac but APFS is better), erase the thumb drive as exFAT (Master Boot Record, MBR).

Thumb drives are usually already formatted as ExFat, and both Macs and PCs can read them. Just use File>Export>Export nn Photos, and use the resulting dialog to define your terms.

She would probably like jpgs, full size, max quality, and metadata. But it's good to be able to change any of that.

Matti Haveri suggested sending her originals, but if they're heic, for instance, she might prefer jpgs. This dialog gives you the most control.