Any Advice for Crazy Step Sisters??

So basically I know this person and they mean a lot to me. They live with their dad, grandma, stepmom and two little step sisters. This family can be quite lovely to be around and overall pleasant people but there’s a problem. The parenting. The two little ones can be quite badly behaved and they really get away with anything. The person I know is constantly getting in trouble for “yelling” at their sisters. The little sisters will purposely get this person in trouble, make up lies, hit them, you name it. The stepmom tells them not to listen to this person so it’s really hard for them to tell their sisters no to anything. They just don’t listen. I hear about it a lot because me and this person talk a lot and the amount of times I’ve heard “sorry we can’t talk I’m not supposed to be on my phone” or “they’re taking away my phone so I won’t be able to talk” is kinda crazy. This is the sweetest, kindest most caring person I know. This person doesn’t need the discipline the little ones do. This person gets quite frustrated as anyone would. Any advice I could give them?