[[Should I Tell My Mom About the Pics?]]?

Well My lil sister was on my laptop && she left her loggin open && it was on her yahoo && it was emails to random people saying here are pics of me... && crap like that well i clicked on it && it was pics and of her l area && she dosent know them. i mean ive known for a while that she talks with people that she dosent know on mysoace && talks about gettin together to have buh i dodnt think she was like that... Should i tell my mom shes been putting pics of her on the internet to random people? i mean she knows i have taken pics && i have with my boyfriend buh its stickty between me && my bf. && weve been together for years && im older buh shes just startin high school. && she just turned 15.... my sis && i have never gotten along && the past week we havent fought once && we had slumber parties together && everything. and i think if i tell my mom that it will ruin our relationship... i know telling my mom is the right thing.. buh im not so sure.