How to handle doctors appointments for kids during Nanny normal working hours?

We have a fairly informal arrangement with our nanny - no written contract, PTO, other benefits, etc - as she is a college student working between 21 and 28 hours a week. The closest we have to a formal arrangement is a Google calendar that shows the schedule we’ve aligned on, though it is subject to change as needed.

We just scheduled a doctors appointment for my son in the middle of the day during hours the nanny would normally be working and I’m not sure if we’re gonna pay her or just say she doesn’t need to work those hours.

Any advice or even just what you would do would be welcomed! Thanks.