Yastremska beat Linette 6-4, 6-4 in Saturday's semi-finals before Kessler defeated Slovakia's Rebecca Sramkova 6-4, 6-2.
The world number 46 broke Linette in the fifth game of the match and held her advantage to take the opening set in 45 minutes.
Yastremska, 25, raced into a 4-1 lead in the second set before a rain delay forced her to wait to clinch an impressive victory over the world number 31.
Kessler, ranked 42nd, needed just 70 minutes to dismiss Sramkova.
The 25-year-old took the first set with a break in the 10th game when Sramkova double-faulted on set point.
Kessler went for the kill as she surged into a 4-0 lead against the world number 38 in the second set before serving out the win.