Good quiz but, I only got Margaret Court when I entered Smith for Stan Smith. Yes, that’s her married name but she’s far more commonly known as Margaret Court, so perhaps you could accept ‘Court’ as well.
I think you should reconsider the country which you’ve placed Martina Navrátilová under. She won every single one of her GS singles titles under the flag of the United States. Of her 59 GS titles, she won only won one doubles and one mixed-doubles title under the Czechoslovak flag.