Of course your wife hasn't gone mad - it's you!
If you always ensure the kettle is empty before you use it, then you can take it to the tap and only fill it with the amount of water you want to use.
You seem to be making a mountain out of a molehill with with your statement:
'If it's something stupid like £3.77 a year then why am i going to go through the hassle of walking to the sink filling the kettle, walking to the kettle switching it on, then remembering this energy saving tip, so switching off the kettle, walking back to the sink pouring half the water away, then walking to the paper towels to wipe of any excess water then walking back once more to the kettle again to switch it on?'
The only proviso I would say is, check with your kettle's instruction booklet and find out what the minimum amount of water should be put into the kettle.