brother and sister relationship | ADHD Information

To start off im 22 and my little sister is 15.

My little sister was always hyper since birth.  The doctor always supected she was ADHD. When she was 7 she was offically diagnosed. When she was 13 she started experimenting with drugs and alcohol. She also abused her ADHD drugs. When she turned 14 her behavior got worse and she ended up getting expelled from school. During the time she got expelled my parents had a big fight. My mom told my dad you take her, i cant control her shes a problem child. So she lives with my dad and i live in my own appartment. This year (15 yrs) my dad sent her to alternative school. She started Tuesday and i asked her how it was. She told me she loves it because the kids are just like her and you can curse and do whatever you want. no one says anything. I had a very hard time believing that. I asked her why she is acting this way and all she said was im not a bad person i just make bad choices. Then she called me last night and told me shes outside my appartment door because she had a fight with my dad and ran away. I told her to come in and when i turned around to look at her her face was wet and she was crying. i asked her what happened. she said dad saw me kissing a boy and told me i was easy because i only met the kid three days ago in alternative school. she asked me if she could spend the night and i called my dad and he said it was ok as long as i drove her to school today. i just DONT get why shes like this. She makes bad decisions and then only comes to me crying when she is introuble. My dad said she needs to learn things the hard way. but i cant help it whenever i see her standing there crying i want to go up to her and hug her tell her everythings ok. Im really afraid she will end up getting killed or end up in jail because of a decision she makes. i dont know how to help her. and tell her turn your life around. what can i do????