cello! i love the cello. absolutely. it has the warmest, most emotionally evocative sound of any of the stringed instruments. cello players are also a different breed, maybe this speaks also to her personality... a bit of a rebel maybe? A little Jacqueline du Pré in the making?
i think its awesome that you foster music in your kids. and by the sounds of it, your daughter is really into it, hell if i practiced as hard as you describe when i was 9, i probably wouldn't have to work a day job!