I have a 14-year-old sister who my grandmother and I are gaining custody of. I don't doubt my grandmother's ability to take care of and discipline my sister the way she should be, but she and I are unsure where to start.
My sister was living with my mother who is mentally unstable, who did not discipline correctly, her mother would scream, go into hysterics, cry, threaten violence on herself or my sister anytime my sister acted up or even times where she did nothing wrong at all. Because of this my sister does not understand certain actions have consequences, my sister believes if my mother didn't find out about whatever it was she was doing then she wouldn't get into any trouble. This is not true because my sister's actions could negatively impact her future but she hasn't been taught that, just fear instead.
I have found out my 14-year-old sister is drinking, smoking weed and having sex with her boyfriend. I am horrified and want to get her back on the right track but I don't know how to start. If I ban her boyfriend I am afraid she'll run away or shut down on me and not tell me anything. I want to show her my grandmother and I are here for her and she's safe in our house and get rid of her unhealthy coping methods she's picked up from her mother. I'm taking her to get birth control and I will closely monitor her time with friends she may be engaging in these behaviors with.
What is the best approach to begin getting her back on track and how do I properly teach her consequences and discipline?