Here are some health benefit options besides a traditional health insurance plan: https://gtm.com/household/resource-center/health-benefit-options/. You could offer a tax savings plan like a QSEHRA which you fund tax free and your nanny can use to buy health insurance even if they are on a spouse's plan.

You can still get insurance on the ACA exchange but you have to act before the end of the year.

We are looking to purchase health insurance for our nanny in VA -- I don't know where to start!!! Any tips or info anyone can share? Thank you!