I am a big big fan of this holster! I can wear normal (tightish) t-shirts with absolutely no printing in the Appendix position. I have 3 other holsters and none of them conceal as well as this holster (printing is a big issue for me as I am slim)
I do have 3 issues with it though:
1. Raven Concealment said it fits ALL M&P models. This was untrue as it does not fit the Bodyguard or Shield (which is what I have). After I complained they updated their website but would do nothing for me as far as restocking fee or shipping costs to return it. So I had to modify it myself but it now fits perfect.
2.Very hard (and I would say almost dangerous) to re-holster unless you snap off the holster from your belt and attach it the the pistol before reinserting into your waistband.
3. They have a lanyard string hole that juts out of the end of the holster. It dug into my thigh/groin when sitting down so I just trimmed it off.
With that being said though, it is probably one of the best concealable holsters out there for Glocks and M&P's hands down! I'm sure your wife will love it!