Serious help please !!?

my ex boyfriends little sister is a mess. she's been expelled from school, shes rude, disrespectful, rebellious and shes only 15 years old. his mom is asking me what she should do and i really have nothign for her. just yesterday they got in a fight and the girl left the house at 12:30 am and didnt come home. she went straight to school the next morning. ive suggested boarding school but she can't afford that and they're from Colombia so suggested sending her away as well but, she doesn't want to put that stress on the family over there. please guys. we really need your help/ any suggestions will be just fine. we're desperate "/