She lives alone, with reasonably good health for her age. She's always been prone to story-telling, but she's progressed to paranoid delusions, blaming neighbor for drilling holes in wall and drugging her, claiming she hears conversations from neighbor plotting to harm her, has already called 911 because she feels drugged, checked out at hospital and been released, constantly calling apartment office with complaints. She's very worked up and believes every story she tells. She's frightened. Calls family middle of night telling us to come right away and bring police. Family doctor referred her to neurologist. How can family help?
While you are waiting, in general it does not help to argue with someone who is having delusions. I don't think you want to agree with her that the neighbors are plotting against her, but try to reassure her. "Mom, hearing that must have been really scary! I don't blame you for being upset. We've known those neighbors for a long time, and it is hard to believe they are plotting anything. I'm sure that whatever snippets of conservation you heard sounded like a plot, but if we knew the whole story it would turn out to be more innocent. Do you want me to talk to them?"
This is not at all easy. The idea is to sympathize and reassure, without telling her she is right.
The apartment office has probably figured it out, but it might be a good idea to have a chat there and explain that you are trying to get some help for Mom. Also, do you suppose Mom would let you handle her complaints? She could write them down and then you (or a designated family member) could "handle" them for her.
I hope her appointment with the neurologist is soon! She is miserable and this is disruptive to a lot of people.