You need to go to a well-supplied gun store, and have them handle a bunch of guns including 12 gauge.
The ergos will tell them what they like.
As an example, I had picked out a couple of 20 autos for my daughter. I let her go down a rack of shotguns and play with all of them. When she grabbed a 12 gauge Benelli Ultralight, she immediately said "this is the one." Nothing changed her mind from that. The price is out of my range, but at least she knows what she wants.
