Teen rebelling : advice needed 💔❗️

My 14 year old sister in law has been skipping school, smoking weed, having sex, doing drugs and Idk what else. Can any mom here give me and my mother in law some advice. We just found out about all this yesterday. I am still in shock. her and I were close or so I thought, and I never saw this coming. I want to help my MIL out she seems so devastated any advice would be appreciated. Homeschool? Boot camp? Anything. We were all planning her 15th party but that is now cancelled . Today after dropping her at school I called to make sure she was there but she has been marked absent all day