Or you could offer to let her stay the night at your house.

Let her use the guest/spare bedroom or even let her sleep on the sofa.

We put our nanny in an UberX at the end of the night if we ask her to stay 2 or more hours late and it's not Friday (i.e., if she has to be back to work the next morning). It's about $40, but she otherwise has a 1.5 hour commute back on public transport and I don't want her unhappy and exhausted to take care of my DD the next day. It's worth it to me to use our normal nanny rather than a sitter, even though I could avoid the $40 charge w/ a sitter.