In The Tale of the Heike, written at the beginning of 14th century, she was described:
… especially beautiful, with white skin, long hair, and charming features. She was also a remarkably strong archer, and as a swords-woman she was a warrior worth a thousand, ready to confront a demon or a god, mounted or on foot. She handled unbroken horses with superb skill; she rode unscathed down perilous descents. Whenever a battle was imminent, Yoshinaka sent her out as his first captain, equipped with strong armor, an oversized sword, and a mighty bow; and she performed more deeds of valor than any of his other warriors.
Source: Onna-bugeisha – Wikipedia