Coco Gauff has made it through to her first semi finals af the US Open after defeating 2017 French Open champion Jelena Ostapenko, 6-0, 6-2, on Tuesday. Gauff, a 19-year-old from Florida, is the first American teenager to reach the final four at Flushing Meadows since Serena Williams was the runner-up to her older sister, Venus, in 2001. This was the 16th victory in her past 17 matches for Gauff…