The success marked Maria's first win of the season, a week after she was defeated by 17-year-old Emerson Jones in the first round of the Brisbane International.
"For me, playing against her was an honor because I've never played against her before. It wasn't easy with the strong wind, but it was amazing," said Maria, as quoted by the WTA.
Williams and Maria's first meeting produced the oldest age combination in a WTA tour match since the tournament was founded in 1973, with Maria competing at 38, while Williams was 45.
The mother of two broke Williams' serve five times in a victory that lasted one hour and 27 minutes, using her slice-heavy game in windy conditions in Tasmania.
