Your sister is in an abusive relationship. It is hard on her, and it is hard for all those who love her.
Here is the thing. No matter how much you may be right, You cannot make her leave him. He has conditioned her to believe that this is how they "love" each other. It is not consistently bad. Abusive relationships have cycles. Honeymoon phase, plateau stage, downward spiral, explosion, misery phase and back to the honeymoon phase.
Her life revolves around this horrible cycle. You probably get her calls during the misery phase. But she lives for the honeymoon phase. This cycle makes her think things like "Other people do not understand what we have." "I still love him". " He is not all bad". "This is the way he loves me"'.
The thing is while you cannot make her end this cycle, you can choose not to live this cycle with her. If you are not in the mood to listen to her misery, tell her " I cannot listen to this today. Let us talk about little Timmy instead". Or "You know what feel about this. I think this is something you need to handle in the way you know best." And then make an excuse and say goodbye.
When you are listening to her, don't listen with the heart of someone wanting to fix things. Listen with the heart of someone who pities her. Her pain is real. Her inability to leave is her inability to see past her miserable cycle of "love". She is addicted to the pain, the drama, the high and the low of her ugly relationship.
You can say things like, " Wow, I hear you. do you think what he did is normal behaviour? What do you want to do about it?" Or "You said he dumped the plates in the bin after he decided your cooking was too salty. Do you like to be treated that way? What do you want to do about it?" Or " Yes, not doing anything and accepting this is your life is one option. Will that make you happy? Do you think there are other things you might be able to do that could make you happier?" Push everything she tells you back at her. Make HER think of an action for herself. Don't be her dumping ground. Be her mirror. Reflect everything she says back ar her. If her action is to wallow in her own misery pit, make sure she knows that this is the choice that she made.
You didn't ask for it, but (((big hugs))) to you. Dealing with an abuse victim is painful and difficult. It is so much harder when it is someone you love. Best of luck.