Congratualtions on your new purchase.

As a possible alternative to going with a smaller bore for smaller people you might look around for 'low recoil' rounds. These are sometimes marked as 'low recoil-low flash' rounds. They are popular with police agencies that may end up with smaller framed men and women using the 12 gauge and who have an interest in protecting their night vision.

Essentially they are just standard round with a bit less powder in them. Just enough of a reduction to take the edge off the kick without seriously compromising the velocity. It also means you don't have a two foot long flame coming out the muzzle.

Most people don't notice the blast or flash much until they fire the shotgun in a dark and enclosed space. A standard 12 gauge round fired in a small room can temporarily rattle, deafen and blind everyone present.

It is good practice for everyone concerned to try it inside a few times to get used to this blast. A cooperative indoor range is handy for this but it isn't too difficult to rig a backstop and get a feel for it at home. I will leave the logistical details, and finer points of negotiation with the lady of the house, up to the reader. But remember that even if she loses the argument she will, by design, end up a loaded shotgun in her hands in the process. So play nice.