The known facts are that Kay lived in New Hampshire with her parents, and Michael went to Dartmouth, which is in New Hampshire. So they met in New Hampshire.
But when?
I'm guessing that Michael had enrolled in Dartmouth before Pearl Harbor. As a New York State resident, Michael would have been 17 or 18 when he graduated high school. If he was 21 when he enlisted in the Marines, what was he doing for the previous 3 or 4 years? Probably studying at Darthmouth. If so, he could have met Kay at any time during those years before Pearl Harbor.