Ok, you guys are thinking too much like a detectorist, and not a husband who's wife is just wanting to connect with him in his hobby just to be able to spend more time together, first thing you have to consider is...she could give a rats patootie if she finds a gold coin or a beaver tail, first thing you have to do, is make it easy for her, a detector that doesn't need much setup, a turn on and go, maybe a Whites coin shooter, A Garrett Ace 250/350, something you can setup, easy to identify targets, she doesn't need to dig 12" targets for that elusive coin. Second, don't set her up and then set her on her way another direction, Find something, have her re-scan with her detector, both of you dig and find it together. If you truly want her involved and you're not just using detecting as a way to "get-away" as someone suggested, talk to her to see what would peak her interest enough to want to be with you while detecting, and either she'll get the bug or she won't. But either way, make it fun for her. Then schedule some days maybe where only you go, she won't mind if she isn't a "Detector widow". Another thing is create an "after detecting" event, after you're done digging, a nice lunch or dinner afterwards, gives her another thing to look forward to when going detecting.
Just my 2-1/2 cents, I love my wife and do anything for her, and would never let her feel alone while I'm having fun, might have to join in one of her hobbies to reciprocate...hows your needle point lol.