Hi Sandie: I can't help with 1930 census for a few days; I only have access to it at the library.
But I decided to look Lily up on the Ellis Island site. Lily says on the 1924 manifest that she'd been in the U.S. between 1921 and 1924. I couldn't find a 1921 manifest with her on it, but not all New York passenger lists are on the Ellis Island site, I've found. Or she may have entered through another port in 1921. Philadelphia, Boston, Baltimore, perhaps.
In 1924 she apparently returned to Devon to visit. The manifest lists her father Henry Best as nearest relative and the address is 15 Selborne Villas, no town though. The manifest says that she was going to visit a friend, Mrs. Bull at 875 6th Avenue, New York.
Perhaps none of this is new--unless you didn't see the second page of the manifest (on the Ellis Island site the two pages are actually in reverse order, with the second page appearing first. Just click the "Next" when you see the miniature manifest). I thought I'd post it as I was reading.
Cheers,
John