What should I do?! Thank you in advance!

So my sister and I were adopted by our aunt and uncle a few yrs ago & I moved out 2 1/2 yrs ago because we faught all the time. So my sister stayed there. Now my sister is always txting(it's been at least a year) or calling me saying my uncle is yelling at her or screaming about whatever it is she did "wrong" which half the time, it's over nothing and he's over reacting. Well me and my fiancé told her that she could move in with us and she wouldn't have to worry about that but she would have to go to a different school because hers would be too far for us to take her. She told us no because she didn't want to leave her friends and I told her fine. The offer is open. So then today she texts me and tells me she's gotta pay $850 for messing up my uncles trailer and that she's so tired of the fighting and over it. I reminded her that she was the one to choose her friends over coming with us and she got mad. I get really upset when she texts me and it makes my fiancé mad because I raised her and this is happening constantly and stresses me out. So basically my question is should I just tell her to not txt me about this issue anymore, keep letting her rant to me, or say something to my aunt and uncle myself. Thank you so much for reading this and helping me out!