Chuck
Although your experience turned out OK, I don't think I would've done it.

Something didn't make sense. Walking from Ripon to Berlin in the middle of the night? "Why" is what I would've asked myself. And now that I read your follow-up story, I would've said "no thanks", and told her that I will be glad to call the sheriff (or whatever local authority) and arrange a ride. I would've instructed wife to be calling 911 or similar while you were talking to her anyway. 

I can't see that anyone would think that was a reasonable request from her....showing up at your door and asking for a ride though she had set out to walk the distance. How long would it take a 15 yr old to walk from Ripon to Berlin? 5 hrs?