"Why, why, why, does my missus want to invest in gold now?"
Not wanting to be sexist, but...
In my experience a female significant other will not believe or listen to anything you tell or explain to her using reasoned argument and logic. What has happened is that one of her 'enlightened' friends has mentioned gold in passing and so she has now has confirmation from someone with 5 minutes experience on the subject, so she thinks you must be right after all!