Need some advice

So recently my 14 year old sister has been staying with me my fiancé and our 3 month old. she has been having issues with my mom basically going through the same thing when I was around that age (also the reason why I moved out at 17). My mom would talk to me about her behavior quite often anytime she has done something wrong, not helping around the house and in their terms what happens when she’s not “boss” and I would give her some suggestions but she would NEVER take it and it was always from my moms point of view I never hear my sisters side and what the leading cause of it all was after her staying with me a couple days and talking about everything it is completely different and adds up to why she has reacted and didn’t do the things my mom had said, But What sparked this fight was my sister went to the school counselor and told her about how she was feeling and about the issues at home even prior to all this it has been building up. My mom flew off the handle cause the school notified her, she then agreed to get her a counselor to help her get help but instead of getting someone professional they went to the church they occasionally attend and talked to a lady who works at a state hospital. Me n my mom hasn’t been on talking terms bc when my 3 month old was born she hasn’t made an effort to see him as much as his fathers family has and they live farther then my family does, so we have been having issues and my sister wanted to come over one weekend and spend the day get away for couple hours well that opened a whole new can of worms, it came down to my mom had told my sister to come stay with me for the next 2 weeks, in the last few days it has been nothing but arguing. Her telling me and my sister through text that I am responsible for her and that i will be taking her to her upcoming dr appts so on and so forth, So I need help on what to do since we live in Missouri and she is 14 she can’t decide on her own where to live. I’m at cross roads bc I feel like she shouldn’t have to be made to go back, my mom is not like this with our younger sisters either. I want her to be happy and to get professional counseling and for her to focus on her school, to get into college. She refuses to even think about going back home and I’m not going to force her either. I need help🙏🏻