I'm pretty much in the exact situation as you are... except the direction of where I'm firing. I've pretty much concluded with help from this forum as to sticking with the 9mm so I can draw my wife into shooting and being ok with them. That is if I don't find my 357 gun I use to have, in that case I'll have to buy her her own gun. Which is a win win since I'll get a 9mm and my old 357.
I was really considering the 40, but based on everything I've read since I want her to buy into the whole thing the 9mm probably would be easier for her to deal with. She is pretty anti-gun, but the latest changes in laws and politics combined with the economy makes it almost logical to get one.
Good luck with your decision, I'm hoping within a week to get mine.