Is it safe and helpful to tell my client how she acquired her breast cancer? She is saying God gave it to her.

This is not a danger compared to telling her how she is being targeted. So having her caught up in a worldwide corruption intended to harm many innocent victims is true and puts the blame where it belongs. Whether she will believe this and whether it will raise further doubts in her mind about you is another concern. She is not there yet with respect to things you have taught her about the wider world and the evil things happening. It is one thing to believe there is darkness and another to attribute it specifically to an Extraterrestrial Alliance, but we see everything here is dependent on her continued growth and learning because that is, in part, what is necessary to happen for her to make her way out of the hole she is in.