Sounds like your wife is actually trying to help you. You should let her...
What you need is a good strategy. You have a great opportunity each time she breaks something, you just need to capitalize on it. Here is what I'm talking about:
Example #1. You want new winches but know your wife would never approve of that much money spent. While sailing, she breaks or throws the winch handle overboard. So, you buy a new (and very nice) winch handle along with new primaries. When she complains, you only have to point out the two were next to each other in the catalogue and you weren't sure if the new handle would fit the old winches anyway.
Example #2. Your wife breaks the throttle handle. If the handle is part of the binnacle...and a wheel autopilot mounts to the binnacle...and there you have it, your troubles in talking her into an autopilot are over!
Example #3. Your wife breaks the ignition mount. The ignition is part of the electrical system...the electrical system could use an additional house bank...the new house bank will need a new battery switch...battery switch and ignition switch are both switches, so the pattern is now circular and complete.
I don't think it'll take her long to figure out what's going on and take more care when operating the boat.
I guess I should warn you though that I've been divorsed for 17 years. Thus, I'm probably not the best guy to take this advise from.
Hope all turns out well.
Skipper, J/36 "Zero Tolerance"
I really like the way you think.