An easy "fix" that worked for me was a two step approach:
First, I made a production of removing all the A/C vent covers, taped under them (something I'd planned to do anyway) and announced to the DW that moving them would make them leak and make it hot inside the trailer...
Second, (and probably the step that really fixed it): I took her step ladder out of the trailer and hid it in the rafters in the pole barn. She looked for it several weeks, then finally announced, "We must have left the ladder at a campground somewhere, I can't find it." So far, I've never acknowledged her remark, so I suppose (at least in my mind) that I didn't do anything "mischievous" or "underhanded"......