In 1989, Stefanova won the Girls U10 section at the World Youth Chess Festival in Aguadilla, Puerto Rico.

[6] Stefanova was awarded the title of Grandmaster at the FIDE Presidential Board meeting in Doha in July 2002 as the ninth woman to ever have reached that rank.

[10] Stefanova became the tenth Women's World Chess Champion in June 2004 by winning a 64-player knockout tournament held in Elista, Kalmykia, under the auspices of FIDE.

[11] In 2008, she won the North Urals Cup in Krasnoturinsk, Russia,[12] and the women's individual rapid tournament of the 2008 World Mind Sports Games in Beijing.

[14] In November 2023 the Bulgarian Women's chess team with Stefanova as captain won the European championship.