I corresponded with an expert on terminal performance, Dr. GK Roberts. According to the tests he performed, frangible ammo is not good for self defense. Doc's tests also show that birdshot is a poor choice and #4 buckshot as a minimum.

goodoboy, I'm starting to feel like I'm casting pearls before swine. It's your money, it's your life. I've given a few fish and tried to point you in a direction to learn to fish for yourself. Read the following-

http://www.mlefiaa.org/files/ERPR/Te...erformance.pdf

Let your wife shoot the AR. Then let her shoot the shotgun and see which she prefers. I bet you a box of bullets, or shells, she'll prefer the recoil of the AR.