Stefanini broke for 5-3 to seal 6-3, with Yastremska's resilience a 7 minute hold for 1-1 saving both break points.
Yastremska broke for 4-2 and again for 6-4, clinching the set despite Stefanini's break for 4-5 in a deuce game.
Stefanini broke for 2-1, 4-1, and 6-1, dominant after a 6 minute hold for 1-1 saving the sole break point.