There are 2 border crossings from Canada to the US from 1940 & 1941 for Gertrude May Williams born Summerhill, Wales. They are hard to read, but it looks like she was working as a cook and her contact in the US was a Mrs. Crawford, 5-something Park Avenue, New York City. Her brother Edward is listed on one of the pages as living in Toronto.
I think she is with Adele G. Crawford at 580 Park Ave. as a cook on the 1940 census. An obituary for Adele's husband William says he was the head of the building firm William Crawford, Inc. in New York City and died in Southampton, Long Island.
So, I don't see any Rockefeller connection, but a pretty fancy address nonetheless.