If Nanny is babysitting do I pay over time ?

Current nanny works full time M-F guaranteed hours/ is on a payroll for us. She will babysit on the side after she leaves us during the week or weekend.

I have an event on a weeknight at 6:30pm and will need a sitter for 1 hour. She typically leaves our house between 4-5pm. She lives about a 20-30min walk from us.

Legally if I ask her to babysit do I need to pay overtime or can I pay regular rates?