The 54th-ranked Spaniard is 4-1 in finals after winning in Bogota and Bastad in 2009 and Rome last year. All her victories have been on clay.
"It's a really good step for me to play a lot of matches in the same week and build my confidence," Martinez Sanchez said.
The 109th-ranked Mayr-Archleitner, who routed the 8th-seeded Ksenia Pervak 6-0, 6-0 Saturday to reach her first career WTA Tour final, won just four points on serve and nine in total in the opening set.
The 28-year-old Martinez Sanchez, playing her first final this season, had nine aces and won the first seven games. However, she was 4-1 down in the second after dropping serve twice.
She saved six more break points to win six of the next seven games as her opponent seemed to struggle with the strong wind during her serve.
Reaching the final means Mayr-Archleitner, who was a career-high 70th two years ago, will return to the top 100 when rankings are updated on Monday.