Alisa Weilerstein is used to leading a double life. As an accelerated high school student, she was already a concertizing cellist who lugged her unwieldy instrument on and off trains and planes. As a Columbia University undergrad she wrote philosophy papers while airborne, traveling from one performance venue to another. But make that a triple life. The 28-year-old New Yorker, growing toward a stellar career, is also diabetic and has been since age 9 — all of which makes her over-achievement understandably remarkable.