And the facebook pages of nearby towns, if she is able to access.

Go to her town's facebook page and ask there.

I was walking on Main Street Dobbs Ferry and happened to see a business called Family Helpers. Maybe try that?
https://familyhelpers.com/

There are Facebook groups like Childcare in Westchester. A lot of this has moved off of care.com to Facebook.

Would she be ok with a college student? Maybe she could put up an ad at Mercy College?

I live in the DMV and am trying to help my sister who just had twins. All her contacts are telling her to use Care.com but she’s not having much luck. Are there any other options/ideas? Thank you!