<human>: I've been living with my adoptive family for about 6 and a half years and everything was fine. I've always enjoyed my time with them (mom, dad, 1 sister and 1 brother) but recently my adoptive sister has changed.

Like last night, when I called dad "dad" she asked why I was calling him dad. I always called him dad since he is my father figure. He wasn't happy about what she said and neither was mom or my brother. It's only an occasional thing (3 times a week at the most) and it just hurts cuz we used to get along well.

I guess what I'm asking is this, how should I react? Like I don't hate any of them and I won't pretend to. But when I try to talk to my sister she just walks off or doesn't listen. It just makes me feel left out. I'd like to hear other people's opinions on this and how they'd react if they were in my position. Thank you for reading this.

Give me the gist of the text in a nutshell
<bot>: My adoptive sister makes me feel left out and is mean about it and refuses to communicate with me. How can I try to resolve this?