Upvote:3
The official story on wikipedia and a few other places appears to be that they did not meet in 1917, but were rather married in 1917. The story I seem to find about their meeting was that it was at the home of a friend (Samuel Bonchek's) in New York in 1915.
I did also find a bit about meeting at a Trotsky lecture too, but it took some searching. That work lists two references: Ben-Gurion, The Armed Prophet and Memoirs - David Ben-Gurion, so if the author wasn't repeating a rumor, the story may have from one of these two sources.
I can find no discussion about this matter on his wikipedia talk page.