I am wondering what do you do when your mother has allowed one of her kids to take over so much that I’m not even involved in her death?

How can I say this and not sound mean? You sound a lot like me in many ways, but growing up my sisters lied, cheated etc all the time and I SUFFERED THEIR PUNISHMENT.
What does executorship "allow" your sister to do? She can't do diddly until after Mom passes. Has she forced your Mom to hand over money, property basically abusing your Mom financially? Does she live with Mom, controls who comes/goes? Does Mom have a Will? Was it done through her attorney? Consult the attorney and Express your concerns about what your sister is doing.

Step back. As my daughter likes to say "not my circus".

When Mom passes and if ur beneficary then you can ask for an accounting of where Moms money went. If its found sister stole it, she will get less or owe you. Executorship is looked at by the court. Her responsibility is to pay Moms bills before any money can be split. And that has to be done by how the Will reads. If u get nothing, let it go.

So sorry this has happened to your family. Are there any other siblings? If not, is there a family pastor or family lawyer who would gently intervene for you? I hope you can keep a relationship with your mother & sister, even though they're being unfair to you now. This also happened to me, in the 90's, when sister convinced mother I was only interested in her money. That hurt, & the next year my sister died suddenly. Even worse, mother never even called me when they 'pulled the plug' on sister's ventilator, (nor did my mother allow me any of sister's possesions). 23 yrs later, I was the only one left to take care of mother, which I did for last 6 years of her life. Good luck, I hope it ends better for you than for me.

I don't honestly see anything that you CAN do. You are correct, that when money comes into it families often fall apart. I would not waste time on it. I would go on with my life. I would simply say that I love them and I wish them luck, and they should contact me when there is something they need help with; I will see if there is some way I can help (or not). Then I would go on with my life. You will not change them by argument. You will not change them by anything at all. So just move on. People do change. Not always in a good way. You could, before you "leave the scene" say that if they would like to meet in family conference with a psychologist or a licensed Social Worker trained in helping families work together, you would be more than willing. Then just move on. No argument. No trauma-drama. Just get on with your life and make it quality.