How to connect with my sisters

My sisters had a not so normal childhood. I have 4 sisters and I am number 2. My oldest and youngest, lived with my mom but then my older sister took my little sister in as she was starting middle school and took care of her until she graduated, up until now. That shaped and affected their relationship. Lost story short, my younger sister feels like she is alone in the world but she has a really nasty attitude about it. Unappreciative and just down right mean. If something doesn’t go her way the whole world is against her and you can’t prove her wrong.

Recently we got into an argument because she asked me to help her with something but in actuality she wanted me to do the whole thing for her and I told her I would help. Well my plan to help didn’t work out and she got upset because I could have just did it her for. Well the next day she got upset at my other younger sister and I for not saying hi to her when we each got home. I tried to talk with her and it just went south. What I am looking for is a way to connect with her but to also help her understand that her nastiness pushes me away. I have learned to keep my peace and care about my sister but she disrupts that peace. What can I do?

Thanks is advance everyone!