Patricia Birdway

Patricia Birdway is the younger sister of Leivinia Birdway and is a supporting character through the various Toaru Majutsu no Index novels. Her appearance is somewhat similar to her older sister, as she has short blonde hair and blue eyes. She wears a track suit consisting of a light-blue jersey and spandex slacks, along with a white vest. She also has headphones hanging from her shoulders. She is apparently not involved in the magic side and isn't aware that her sister is the leader of a cabal. She is close to her sister as she knows various things about her.

(Source: Wikia)