Hi Rebecca,

Paranoia is not necessarily a sign of schizophrenia and before you even get to that point there are a number of other things to be ruled out. A doctor would first want to rule out that your family member is physically ill as some illnesses can mimic psychiatric conditions. 

Are you certain that your family member is hearing voices? Sometimes when people are very upset they 'rehearse' situations aloud and play out different scenario's in this way. If there are no signs of thought disorder or any of the other things you might normally associate with schizophrenia you may find that what you are seeing is a form  of stress reaction. This is just idle speculation on my part but I'm just suggesting there are a number of other possible reasons for why your family member is the way she is.

In times of high emotion rationality often goes out of the window. Given the fact that your family member seems fine with other people might it be worth spending time trying to uncover why it is she feels the way she does about her husband?