I agree with this thinking. Yeah, your pack will be uncomfortable initially, but it will quickly improve. Your wife's happiness will remain high, though.
One of the best trips my wife and I took, I carried darn near everything. All she had was a light Camelback (Golite, actually) with snacks, rain gear, and ditty bag. Her pack was like 4 or 5 pounds. I was only carrying 20 or 25 myself and like you, the food weight went down fast.
I've found that Amy's pace quickens and her spirits are higher when I carry more and that's worth more than the extra weight I'm hauling.
If your wife is only carrying 13 pounds, even the Jam will be overkill! I fill my wife's pack with high bulk, low weight items like insulation and bags.
Have a good one!