A steadier ground guide to suspicion that has spread past the missing purse. What is underneath it, what to say when you are the one being accused, and how to stay safe. Two things before anything else: if this arrived over hours or days she needs a doctor today, and if there is a gun in the house, move it out tonight.
Notice how much it stings to be the one she's suspicious of. Being cast as the threat by someone you've never stopped protecting is its own specific injury, and it deserves a breath before you try to talk her out of it.
Before anything else: how fast did this start? Suspicion that appears or sharply worsens over hours or days, especially with drowsiness or alertness that swings through the day, is not a behavior. It is delirium until proven otherwise, and she needs to be seen the same day rather than booked in.
A brain that cannot retrieve where the purse was set down will still produce an explanation, and the explanations available are the ones that fit the evidence in the room. The purse is gone. Someone was here. Someone took it. That is a gap being filled rather than a judgment being formed, which is why arguing the facts so rarely works. Delusions are common, affecting something like a third of people with Alzheimer's at some point, though the studies range widely enough that no single number is worth trusting.
The specific forms are far less frightening once they have names. Capgras is the belief that a spouse or adult child has been replaced by an impostor, reported in around one in six people with Alzheimer's and more often in Lewy body dementia. Phantom boarder is the belief that someone unseen is living in the house. Mirror sign is not recognizing her own reflection. Television can stop being a representation and become an event happening in the room. Accusations of infidelity are usually about fear of abandonment rather than about sex.
Capgras deserves its own line, since it targets the person emotionally closest, which is why it lands on you, and in one case series people with Alzheimer's and Capgras were more than twice as likely to show aggression. That makes it a safety matter. If there is a gun in the house, this is the paragraph to act on: someone who does not recognize you and believes an intruder is in her home may act on that belief, and the Alzheimer's Association's guidance is to move firearms out of the house rather than into a safe. The same logic applies to car keys and, if she has ever reached for one, kitchen knives.
One distinction changes what happens next. A delusion is a belief that will not shift. A hallucination is seeing or hearing something that is not there. If she is seeing people, children or animals in detail, and particularly if that began early in the illness, that points toward Lewy body dementia, and the clinician needs to hear it in plain words because it changes which medications are safe.
Then check the ordinary things. Pain drives more distressed behavior than anything else you can fix. Uncorrected hearing and vision loss feed suspicion directly, since a person who hears voices in the next room but not the words will supply the words. Medications belong on the list too, particularly bladder drugs and sedating antihistamines, opioids, steroids, Parkinson's medications, and anything recently stopped, including alcohol.
And one uncomfortable thing has to be said. When the accusation names a specific paid caregiver, check before you dismiss it. Do not leave her alone with that person while you do. Look for unexplained bruising, money that does not add up, and distress that appears only around one person. Nearly all of these accusations are the illness. Not all of them are, and Adult Protective Services through the Eldercare Locator, 1-800-677-1116, is where it goes if you find something.
Look for the cause before you reach for the technique, since most of what drives this is findable.
Write down when it happens, what was going on twenty minutes before, and who it names. If it clusters late in the day, the fix belongs earlier in the afternoon. If it names one particular person every time, check rather than dismiss. And if the pattern changed shape over days rather than months, that belongs on the phone rather than in a notebook.
She still knows you. What has failed is the part of the brain that attaches the feeling of familiarity to a face, and the person underneath is still there and still attached to you, which is why the delusion landed on you rather than on a stranger. Being accused of stealing, or of being an impostor, by someone you have cared for is one of the cruelest things this illness does, and it lands harder because it arrives wearing your own name. It is not what she thinks of you. It is what her brain assembled to explain a gap. For most families this eases over months rather than continuing forever, which is worth holding onto. Tell someone what happened today rather than carrying it alone.