I hope you got it resolved, if you haven't and it's still too heavy for her, I would try selling it on Armslist.com (if it's legal to do so in your state). Personally, I would list it both ways (stock and as configured). My experience is that people ask too much for configured guns. The nice thing about configurable guns is that you can personalize them, and I don't know about others, but unless they have an accessory I have made up my mind that I want, I am NOT interested in other people's customization. That said, I haven't had a lot of luck selling accessories by themselves, but it can be done, and I've also had to throw them in to even trades or sweeten the pot (as others have done for me as well).
Given what you said your needs are for, I would definitely consider getting out of the 590 series altogether and start looking at 500 series options. That is not a downgrade in my opinion. The thicker barrel of the A1 series in particular is going to add weight. You don't have to worry about that in the regular 590 serious, but there are still a lot of lighter options in the 500, 505, and 510 lines. I'd also consider getting a 20 gauge because they'll be lighter yet, and remember, even if she's fine with the recoil, you're going to feel it a little more in a lighter gun. In other words, you may find yourself trading the lighter gun in again, and losing more money, because now it kicks harder. You can surely avoid that with a 20 gauge which is still more powerful than a .44 magnum if you think it's the right option. If you plan on customizing a 20 gauge, however, you may be more limited in your options.
Anyway, I hope this helps if you haven't settled in on anything. Given that you shoot a lot and it's been a few months, you probably already put this matter to rest, but it's something for others to contemplate if they're in the same boat reading this.