The daughter of Austrian former downhill world champion Harti Weirather and former world and Olympic champion Hanni Wenzel clocked one minute and 19.82 seconds to avenge a disappointing season.
Maze, crowned world champion in the discipline last month, was joint second - 0.12 adrift - but the Slovenian remained on course to become the first woman to break the 2,000 points barrier.
She moved on to 1,924 and could reach 2,000 with a downhill and another super-G scheduled in the German resort on Saturday and Sunday.
Petite speed specialist Weirather, 23, blossomed at last after six podium places in the two previous seasons and emulated her father, winner of six downhills in his time, and her mother, who won 33 World Cup races in her career.
While several daughters of former champions are on the women's circuit, Weirather is the first to follow her parents and secure a victory.
Sporting the number three bib, she took advantage of better snow conditions to upset the favourites.
"After 74 starts, victory at last. I can hardly believe what's happening to me," said Weirather, whose career was hampered by a serious ligament injury which ruined her 2010 and 2011 seasons.
"It's been a long road, I spent weeks and months struggling and it's not easy to recover when you hit rock bottom."
Both her parents were in Garmisch to join the celebrations, although Wenzel did not watch the race as it makes her too nervous.
"The emotion is there, of course, but the most important thing for me is that she is in good health. To see her win is incredible after what she's been through," Wenzel said.
"Things have changed radically since my time, the demands are extreme today, especially in terms of equipment and technique.
"It can't be compared to what I've known," added Wenzel, who won a world combined bronze medal on the same Kandahar piste in 1978.
Harti Weirather said his daughter had not known her parents were in town.
"It was better for her not to know we were here to better focus on herself," he said.
American Julia Mancuso, the former giant slalom Olympic champion, finished with the same time as Maze to also make the podium.
- Sports & Recreation
- Harti Weirather
- Hanni Wenzel