Japan-born musician-artist whose works include 1964 book Grapefruit (4,3)
I believe the answer is:
yoko ono
(Other definitions for yoko ono that I've seen before include "John Lennon's second wife" , "Artist (and former Beatle's wife)" , "'She was married to John Lennon (4,3)'" , "Artist who married John Lennon" .)