The 23-year-old was trailing the Frenchwoman 4-1 when she retired, citing a right thigh injury.
The Spaniard faced a tough path on her way to her semifinal, fighting past Sam Stosur in the first round, Daria Kasatkina in the second, and two-time Grand Slam winner Svetlana Kuznetsova in the quarterfinals.
Cornet faces either U.S. Open finalist Karolina Pliskova or sixth-seeded Elina Svitolina, who took out top seed Angelique Kerber in the quarterfinals.
Original author: Ashley Ndebele