I went through this after buying my Tamron 18-400 lens (about $1,000 USA), and again when I bought the 24 mm tilt-shift lens ($2,500 USA), but my wife pays so little attention to my camera gear that she considers all of it a waste of money and doesn't even notice when I add anything. So as long as she gets whatever she wants, she pays very little attention to what I buy. My best suggestion is to just add it to your gear and bring it out occasionally at first, then more frequently later on. "Oh this? I've had it for quite a while, but don't use it much", would be my best suggestion for dealing with this situation.
Now, by having this 18-400 lens, I've managed to cut the weight and volume of my bag. I now carry just the one lens, instead of three, plus a spare body. With this one lens I can get great closeups and wide angle shots, as well as great landscape shots, and everything in between.
Charley