How can I get her to forgive me?

My older sister is two years older than me (15) and she is my only sibling. We have typical Asian parents who dig their noses into our schoolwork and put a lot of pressure on us. Lately my sister has found ever since she entered high school this website called Tumblr. She has been ranting and posting on it. Once she said a post that was like "just finished listening to a screaming match between my dad and sister". I got really irritated because that was personal business. She complains about our family on Tumblr and such. I told her to stop and warned her to cut it out but she didn't listen. I didn't really moniter her Tumblr until one day I saw it over her shoulder.She had gone on a date with a boy who was an Athiest, and me and my mother are both super religious (I am a cancer survivor so my mother and I would know about the powers of the Lord) and it was basically repeating a lecture my mom had given about how she shouldn't follow in an Athiest path. I didn't really care, because she can believe in what she wants, but I did ask her if she believed in Jesus later. Her post was like this : "MA (the second letter of my first and last name) was being super annoying today. She asked me if I believed in Jesus and stuff. The devout Christian she is. o.e" you could sense sarcasm in that. My sister is lazy sometimes, and when I come in to her room to talk to her or when I try to talk to her she kicks me out. She is a procrastinator and goes to a smart people's high school and is/was the top student. She is a sopre. I am pretty smart too and following in her footsteps and all, but the way she acts just peeves me off. She barely helps around the house and I helped her with like two school projects. Her phone broke and i lend my phone to her when she needs it. I always took the blame for her when we were little. Anyways, I got mad at her Tumblr post because it was basically making fun of me (she has said mean things to me to her friends, like how I was "slow" or how I was weird). Now she's probably dissing me. But I told my mom about her Tumblr and she is against all social networking forms so she starts getting mad and yelling. Now my sister is furious and won't talk to me. It's been at least 4-5 hours and I gave her two apology letters, a stuffed dog that says "I'm sorry", IMed her an apology in chinese and english, and basically begged for her forgiveness; i hate it when people are mad at me. I regret telling my mom about the Tumblr and we have Facebooks behind our mothers backs and I am also afraid she will tell my mom about it; i deactivated it and changed the email just in case but still. So have I been a bad sister by doing this? How do I get her to forgive me? It's just that my sister was being incredibly mean and everything I just had to get it off my chest. Thanks. (: