How to deal with my sister?

Male 21 from desi family....my sister who is 2 years younger then me ....she started dating a guy 3 years ago...which obv as in middle class family is not permissible....i caught her messages ...scolded her...but didn't told anyone...not even my mom......long story short... one day my mom called me told me that she's not in the college....my father went to pick up and she wasn't there.......later when she appeared at home on her own.... my parents asked her she told them she was with that guy.......my mom and i approached her nicely and convinced her that we'll take steps for her when the time will come... Days passed .....i was told that she goes out with him every other day...( my mum was hiding this from father but keep telling her to stop this nonsense) . One day when my sis wasn't home i was doing cleaning and i found her diary ( i shouldn't have read that ..basic manners my mistake ) there were inappropriate things there i couldn't handled it... i burned her diary..which i still regret ...but on that time i couldn't.....she came back found the ashes...she picked up a big brick a threw that at my face....luckily i wasn't injured .......but i knew it was my mistake ........we stopped interacting with each other...one day out of no way.....i was served chai tea by her....the time i was served the second i knew something was wrong with it....but i was sitting with my cousins so i took a sip.....and guess what the tea was poisoned......my head started to spin....anyway i went to hospital and got it covered .........how do i deal with it now ??.. If i am wrong please correct me