What is going on with my sister?

My sister is 17 and a senior in high school and she very well might not graduate. My mom has found out that since the begining of the school year she has missed a total of 128 days of school. I don't know if thats entire days or cles added up all together. We found that she has been sending money to some boy in juvi and I myself used to pay her weekly to do dishes and not only me, but our mom and her dad, and grandparents have been duped into giving her money so she can give it to him. My Mom found a letter she had written him and from what it says she knows a guy in there and she talked to his mom on how to wire money and stuff. She has gone to his court hearings and visited him when her dad is doing errands. I think she is in on her friend's mom and she gets her in. My mom has taken her phone away and her car. She has a meeting next week with her teachers along with her dad and my sister too. Thankfully she hasn't told my sister yet so it will be a shock. MY sister turns 18 in august and swears she is moving out. Just one problem is she and her friends shes moving out and none have jobs. My mom is worried sick about it and all the 2 do is argue. She has been like this since she was in 7th grade and it has progressivily gotten worse. I don't know what is my sister's problem. I was never like this at all. I never gave my mom a moments worry so I have no idea where this is coming from. Does anyone know what to do or what her problem is?