Does she have those beliefs consistently? Because if they change every so often, then those delusions are likely to be symptoms of schizophrenia. However, if they are constant and unchanging, she is likely to have paranoia. You should ask your wife if she has schizophrenia or paranoia and if she says she doesn't know or that her mother was never tested, then get it checked out. If she does have one of those, don't do something stupid like set up fake cameras or lizards everywhere. It may seem like fun to you, but mental disorders aren't things that should be used for your amusement. In the case that she is just someone who believes bizarre things, you still shouldn't prank her as it would reinforce her stupid beliefs. Instead just do and say things which would make her delusions seem illogical or leave it alone as it doesn't harm anyone.

Tell her to stop watching Doctor Who.

Spike her drinks older people are more fun drunk

But he IS a shape shifting lizard...

She obviously needs to be referred to a psychologist and a neurologist and mental health!! That's so sad because in her mind she believes that

She sounds schizo. I suggest meds?

They spy on me in the shower too, and to be more specific, its a bearded dragon, and he is fast.

Something is wrong if your milk is warm. Might want a new fridge my friend!

There's truth behind shape shifting reptile human hybrids really do some research.

And all the rude, ignorant people like OP and some of the ones commenting are the reason I'm studying to be a psychologist. It's disgusting how we, as human beings, treat other human beings who are mentally ill. This woman is not a "psychotic wench" as OP so eloquently puts it but someone who most likely suffers from Schizophrenia or some other delusional disorder. She needs support and compassionate treatment and caregivers. People like this don't make any kind of improvement with such hate and ignorance being thrown at them.