Female players who won 3 different slams in the open era (without achieving the career grand slam):
Virginia Wade, Martina Hingis, Lindsay Davenport, Monica Seles, Hana Mandlikova, Evonne Goolagong Cawley, Justine Henin, Angelique Kerber
Female players who won Wimbledon, the US Open and the Australian Open, but not the French Open in the open era:
Virginia Wade, Martina Hingis, Lindsay Davenport, Angelique Kerber (On the mens side: Boris Becker, Arthur Ashe, Jimmy Connors, Pete Sampras, Stefan Edberg)
Female players who won the career grand slam in the open era:
Billie Jean King, Serena Williams, Maria Sharapova, Steffi Graf, Martina Navratilova, Chris Evert (On the mens side: Andre Agassi, Novak Djokovic, Roger Federer, Rafael Nadal)
Kerber is just one French Open title away from becoming the 7th female player in the Open Era to win the career grand slam, something even Justine Henin, Kim Clijsters, Jennifer Capriati, Monica Seles, Lindsay Davenport, Venus Williams and Martina Hingis didn't accomplish. This would also make her only the 11th player (male or female) to accomplish this in the open era.