World number 112 Kristyna Pliskova defeated her twin sister and world number three Karolina Pliskova 6-2, 3-6, 7-6(7) at Nature Valley Classic, in their first meeting in a WTA event to register her career's biggest win on Wednesday. "I think we played the best that we could but it was not easy for us," Kristyna said after reaching tournament's quarterfinals.