Who is Bella Beer from Fugitive Pieces and what is their importance?

Bella Beer was Jakob's older sister. From an early age, she was a serious and accomplished pianist, enamored by the life, career, and works of Ludwig van Beethoven. Bella dressed, ate, and drank like the composer (except for beer) but when she played, she turned serious and precise. Her favorite piece was "The Moonlight", and she often played silently simply to perfect her style. Bella's death haunted Jakob throughout his life.