|US Open 2019|
|Venue: Flushing Meadows, New York Dates: 26 Aug – 8 Sep|
|Coverage: Live text and BBC Radio 5 Live Sports Extra commentary on selected matches on the BBC Sport website and app. Click here for Live Guide.|
The 19-year-old, playing at Flushing Meadows for the first time, won 6-4 6-4 in a match featuring 10 service breaks.
Elsewhere, Dutch seventh seed Kiki Bertens lost to German Julia Gorges.
Bertens, a former Wimbledon quarter-finalist last year, fought off four match points before Gorges won 6-2 6-3.
Gorges, seeded 26th, will face Donna Vekic in the fourth round after the Croat beat Kazakh Yulia Putintseva 6-4 6-1.