No, she was not.

The novel makes it clear that this was an act of jealousy by the other ballerina and that the "accident" was, in fact, no such thing.

At twenty-two, Sonya Moroyeva probably had one final year to move up from the academy to the Bolshoi, but with Egorova in the running that year, her chances were not good. She had been dancing all her life, was the daughter of a full member of the Duma, and was at the core a spoiled and vain young woman. She was, frankly, desperate. She had been recklessly sleeping with a boy in the troupe, blond, lynx-eyed Konstantin, an incredibly risky activity that if discovered by the instructors would have guaranteed their instant dismissal from the school. But after fifteen years in the academy she knew the quiet times, and when the sauna room was deserted, and how long they had for their sweaty sessions, with her supple legs bent over her head, and she whispered in Konstantin’s ear for a week, and told him she loved him, and ground her hips up at him, licking the sweat from his face, and begged him to save her career, her life.

Experienced ballet students know as much about anatomy and joints and injuries as a doctor. Konstantin, rabbit-mad in his gluttony for Sonya’s pizda, waited until he was paired with Dominika. Practicing a pas de deux on a crowded floor, he stepped hard on her heel when she was en pointe, forcing her foot forward, and the colors bled and her world went swirling black, and she buckled to searing pain and total collapse.