how to talk to the delusional

The title implies that I know how to talk to someone who is delusional. I don't. I wish I did.

This is a typical conversation with my sister who calls my parents and I several times a day:

sister: Hi, you fat ugly cunt, I hope you like babysitting R! You are the grossest person I know! How can you be my sister?!!?

me: Hi, I don't know what you are talking about.

sister: Yeah, right! How did you get to be such a fucking ugly disgusting blimp of a bitch?

me: I don't have to listen to you talk to me like this.

sister: Don't you fucking hang up on me! You can turn me off but I can't turn you off, you bitch! Do you think that's fair? How is that fair? Why do I deserve this?

me: It's not fair. I am so sorry you are going through this.

sister: You are not sorry! You did this! You ruined my life! I don't know how anyone can stand you, inbred bitch! You ruined my career! I am pregnant with R's baby and you fuck him!

me: I don't know R! I don't want to know him! I haven't done anything to you!

sister: But you will, you gross fucking cunt! You will! You do it to me every day and then you laugh about it! You're going to get what you deserve, you ugly disgusting pig bitch!

me: This is not real! Please go to the hospital! This is not real!

sister: You go to the hospital, you fat fucking inbred! You are doing this! You have been psychically abusing me for months! Leave me the fuck alone!

me: I want to but you keep calling me! I'm not psychically abusing you - that is not a real thing!

sister: Yes, you fucking are! You don't stop even though I beg you! What kind of cunt does what you have done? What kind of auntie are you going to be, you inbred pig? Or are my kids going to call you stepmom?

me: I guess I'll be an imaginary aunt to your imaginary children.

What am I supposed to say to her? I can't humor her. I can't say I've done things I have not done. I have tried apologizing but that doesn't appease her. Her insane, vicious, vindictive, hate-filled voice terrifies me and breaks my heart. No one should have to endure the torture she is going through. No one should have to listen to the horrible things she screeches at us. My parents always say, "I love you. You will always be my daughter." That just makes her angrier. She gets so upset we are afraid she will have a heart attack.

How do you break a delusion? Yelling, "None of this is real! Go to the hospital! You are really sick!" does not help. How can we wake her up and get her back. None of us can go on like this much longer. My sister has a life to get back to!

We have learned from NAMI and from our own experience over the years that you cannot reason someone with schizophrenia out of a delusion. It does not work. If you argue with them you become enmeshed in their delusion. But we cannot just agree with her, either. We cannot support her madness. So how do you talk to someone stuck in a delusion?