Castello becomes the first debutant since Agustin Tapia in 2019 to reach the final, having beaten two top-four seeds on her way there.
Osoro had played three Master Finals before, but never won a match, reaching her first final since the Madrid Master of 2022.
Ortega and Triay broke at the start of the second set after dominating in the first, but could not see out the contest, meaning Ortega will have to keep waiting to lift her first-ever Master Final title.
Watch the match highlights in the video below!
