From: http://en.wikipedia.org/wiki/Feodosia_Morozova

Feodosia Prokofiyevna Morozova (Феодосия Прокофьевна Морозова in Russian) (1632-1675) was one of the most well-known partisans of the Old Believer movement.
She was born on May 21, 1632 into a family of the okolnichi Prokopy Feodorovich Sokovnin. At the age of 17, she was married to the boyar Gleb Morozov, brother to the tsar's tutor Boris Morozov. After her husband's early death in 1662, she retained a prominent position at the Russian court.
During the Raskol Feodosiya, being a penitent of Archpriest Avvakum, joined the Old Believers' movement and secretly took monastic vows with the name Theodora. She played an important role in convincing her sister, Princess Evdokia Urusova, to join the Old Believers.
After many misfortunes the sisters were incarcerated in an underground cellar of the St. Paphnutius Monastery[1] at Borovsk, where Feodosiya was starved to death on December 1, 1675. Many Old Believer communities venerate her as a martyr.