I'm going to call out my sister to my mom
What are you calling her out for?
She is often rude to me, and she complains all the time.
Maybe you should talk to her about it rather than trying to get her in trouble.
Sometimes I think my sister would be better off dead.
That's a rather extreme statement, you should not wish something like that on your sister. What if you thought that and then something bad happened. Could you forgive yourself for feeling that way?