My wife fits this general category, so her journey:
Started with a Beretta AL390 20 gauge (20 gauge gas gun). Really like it, but after a while started hating the sound/feeling of the bolt cycling.
Moved to a Browning 625 Sporting (28" barrels O/U). She shot it well, but we spent a few bucks and got it fitted to her (S&S Plus in Polson). Not full custom, but changed the LOP and butt angles, plus installing an adjustable comb.
As she started shooting more and more, she started getting beat up by the 20 gauge (over the course of a multi-day shoot). As was described earlier in the post: 1 oz 1200fps 20 gauge and 1 oz 1200fps 12 gauge are the same, but her 20 gauge is ~6lbs, my 12 gauge is ~9lbs. It makes a difference. She tried shooting some of my 12 gauges, and while yes, they made her arms tired faster, they felt better on her shoulder.
She now shoots a 12 gauge Zoli Bella. Not exactly a beginner gun, but she loves it.
At the end of the day, she needs to enjoy shooting it, but you need to be honest about your goal. 25 rounds a week is a big difference than 300 rounds a week.