Well, first off I probably wouldn't suggest to the missus that she lose weight. No good can come of that.
I guess I'd put the bike up on stands and pull off the front wheel and inspect the bearings. I'm just guessing here, but we have the same vintage bike, and it looks like your axle may be backed out a bit. There's a lip on the axle that might account for the wheel being skewed - when the axle's all the way in it can't do that. So if when you pull off the wheel and the bearings look good, I'd apply some grease to the axle and re-install the wheel, making sure the pinch bolts and axle nut are tightened to spec. Then see if everything lines up better.
You didn't hit anything huge did you? Have a look at the rim just to be sure it isn't a bent wheel.
That's my 2 cents worth.
Edit: One more thought - the fender is attached by a couple of rubber bands. Since you didn't say anything, I'm thinking you checked to make sure the fender is in the middle of the forks. If the fender got smacked somehow and the only problem is that IT is out of line, then you've got a really easy fix, just loosen the rubber bands, re-center, and re-tighten the fender.
