Studying at the Bolshoi Ballet School, she won several awards in the top ballet competitions. She received a gold medal at the Moscow International Ballet Competition 2001, First Prize at the Vaganova-Prix Ballet Competition in St Petersburg one year later, and Junior Prize at the Nagoya (Japan) International Ballet Competition.

Graduating in 2002, Semionova joined the Berlin Opera House, becoming the youngest principal in the company's history. She was given the lead roles in The Nutcracker and La Bayadère during her first season, following with the role of Tatiana in Onegin, which became her favourite role.

In 2003, at the age of 19, Semionova performed with the English National Ballet in Swan Lake, receiving approving reviews from English critics. The following year she joined the California Ballet in their production of The Sleeping Beauty, again impressing critics despite what they termed a disappointing overall ballet.

Appearing in Herbert Grönemeyer's music video Letzter Tag, brought her to the attention of the general public.