Astra Sharma made light of a rankings gap of 138 places to beat Ons Jabeur and secure her maiden WTA Tour singles title in Charleston.
19-year-old Osorio Serrano extended her winning streak to eight matches and will meet Astra Sharma in the other semi-final
American third seed Shelby Rogers eased past qualifier Claire Liu 6-2, 6-2 to set up a quarter-final clash against Volvo Car Open runner-up Danka Kovinic