My little sister is stuck at home

My sister is my half sister via our mother. I left the house and moved with my dad after my mom and stepdad had a falling out and my stepdad is the main parent. My sister is a fragile girl who was a lot like me and struggles with ED to the point she needed medical assistance and has self harmed. She told me she feels like she is always being criticized and questioned and so I went to see that side and it’s my first time being here in a long time. Everything was alright with my sister and my stepdad works everyday and gets back around 7pm so we don’t see him much. The moment we get back my sister just becomes stone cold and doesn’t talk or smile. We went out for dinner for a special occasion and I had noticed that my stepdad was telling my sister to smile and stop twirling her hair (she does it when she is upset) she didn’t eat much of her meal but it’s still progress because she ate and I was so proud!!

My stepdad had said “you need to finish your food because people will judge you and draw attention to yourself” I had told him that’s not okay to say that because she will develop social anxiety and it’s not okay to weapon her anxiety against her. He said that I shouldn’t question his parenting style and he needs to be consistent with his parenting style. My sister started crying because she only recently came out to the DR ab her ED. I go to comfort her and I said it’s okay to cry and she blurted out “ITS NOT OKAY TO BE SAD”

Later my stepdad wants to talk to me and he said he appreciates me standing up for her but the world doesn’t give a shit about feelings and so she should put them aside. I told him it’s important for her to express them or she will go back to self harm. She recently just stopped. My sister was self harming from 12-14 and she just turned 15. I am encouraging her to go to therapy but our stepdad doesn’t believe in that.

I don’t know what to do I’m so angry and sad and I hate it here but I don’t want to leave her here. Our mom has a mental illness and she cannot care for her. This is kinda a rant but also reaching out for support or ideas.