Don't see it that way MCH, but expand on your rational on your dislike of that model MB
The girl is recoil shy: This pretty much sums it up, well said Battue
Recoil advantage goes to the gas operated offerings. Reduced muzzle blast, which adds to the cumulative effect of recoil goes to a longer barrel length to diminish blast. If the girl can handle a longer length it will also swing better for pass shooting. If she can’t then the shorter would be a better option.
Pass shooting doesn’t necessarily mean 12ga, if you set up so they pass closer. For a variety of reasons, it may be wise in this situation.
Beretta A400 with kickoff system.
As mentioned, Fabarm Syren for stock dimensions designed for women. The Fabarm also is on the heavy side. If she can handle it, you have another advantage in reducing recoil.
If she is not normal size then something is going to have to be done with LOP. Shooting an adult dimensioned shotgun with a smaller statured person does nothing to reduce recoil or improve hitting
M1 Super 90's are not light recoiling shotguns. I think one of my M1's has over 200,000 rounds through it now. As for barrel being 26" there is no advantage to that once so ever. Longer will always swing smoother and reduce muzzle blast. The added length also helps with the sight picture.