P/t Nanny paid holidays

We agreed with our nanny 10 months ago that we would guarantee 36hours per week (9hours for 4 days) and most but not all weeks need her 4 hours Fridays as we go out of town every few weeks. We also agreed to paid holidays but never went through the fine print and the draft contract we had reviewed with her died with my laptop before I could print it 😬

When a holiday is observed on a Friday, where we had said the expectation for Friday’s is only that we MIGHT need you 4 hours what do you think is appropriate?

I’m thinking pay her a half day, would consider paying a full day bc she’s great but curious what others think. she only ever works 36-40 hours per week so paying for 44 hours bc of a holiday doesn’t make sense right? She hasn’t brought it up, I just don’t want to offend her.