But Thiam pulled out all the stops to shatter her own personal best, racing home in the 800m in 2min 13.00 sec for a total of 6,947 points.
She afforded herself a look over her shoulder as she crossed the line, with Vetter still far down the home stretch, before collapsing to the track.
Vetter eventually came in more than 7sec down on Thiam and had to settle for silver with 6,867pts.
American Anna Hall claimed bronze at Hayward Field in Eugene, Oregon, with 6,755.
Thiam registered 13.21sec in the 100m hurdles, 1.95sec in the high jump, 15.03m in the shot put and 24.39sec in the 200m in the opening day, before managing the furthest long jump of the field, going out to 6.59m, and 53.01m in the javelin.
Reigning world champion Katarina Johnson-Thompson of Britain finished in eighth on 6,222pts.