Your wife will definitely never be late with 15 minutes ahead of time set! I know people that set their watch 5 minutes fast but 15 seems a lot to me.
My wife wears her watch on her right hand also, so I walk on her left - no chance of banging watches! My right wrist is larger than my left and some of my bigger watches look better on my right wrist, but I cannot get used to the feeling of a watch on the 'wrong' wrist.
You are lucky to have a Swiss wife who supports your passion for Swiss watches
Simon