BBC News reports that she then effectively clinched gold with strong performances in the long jump and javelin on day two, before rounding off victory in the 800m.
Her time of 2:08.65 meant she smashed her own British record for the heptathlon, finishing the seven-event competition with 6,955 points, 49 more than she scored in Gotzis in May.
Russia's world champion Tatyana Chernova took silver and Lyudmyla Yosypenko of Ukraine the bronze.
The news agency also reports that American Michael Phelps won the 18th and final Olympic gold medal of his career before he retires as the United States took the 4x100m medley relay.
The 27-year-old swam the third butterfly leg to help the US past Japan before Nathan Adrian brought them home in the freestyle leg.
Australia took the bronze, with Great Britain in fourth.
Phelps ends his incredible career with 18 gold medals at Olympic Games and 22 medals in total.
image: © Marco Paköeningrat
The Alchemists: Three Central Bankers and a World on Fire
Hubris: How HBOS Wrecked the Best Bank in Britain
Sir Chris Hoy to retire and miss Commonwealth Games in 2014
Mo Farah asked by US newsreader: 'Haven't you run before?'
USA Wrestling vows to grapple with exclusion from Olympic Games
Britain's End-of-Year Olympic Verdict: It Was Worth Every Penny
