First,during my career with the Md Dept of Public Safety, I taught hundreds of Correctional Officers to shoot shotguns. Here's a few thoughts on same and Home Defense.
The only folks who ever made it past minimal competence(load and fire w/o horrible accidents or ineffectiveness) were those who liked to shoot and practiced. Maybe half of our officers were only paper qualified.
While other shotguns were suggested and tested from time to time, the only one that demonstrated durability and reliability was the 870. Tower weapons get abused, and the 870s would just keep on working. The old Winchester 97s and 12s would too, but they were and are more collector's items than weapons these days, unfortunately.
So, for Home Defense, I recommend a 20 gauge, since it will be used by a small statured female. Remington makes a Youth Express Model 870 in 20 gauge with a shortened stock and 21" bbl.Choate makes a 2 round mag extension that will add a little weight to the muzzle and tame recoil.Even with the extension, this little 20 handles like an M-1 Carbine
Note, Sidesaddles are nice, but the plain truth is if a scenario is not resolved with 4 rounds of shotgun ammo, what's needed is backup, not mo' rounds.
As for aftermarket bells and whistles....
Lazer sights are expensive and fragile. Folding stocks make sense if you're trying out for Miami Vice II, but not in A-S Scenarios. I'm probably better than most with tactical shooting, but I'd only utilize hip shooting at contact ranges.
Tactical flashlights attached to the weapon have pros and cons. They give the perp an exact location,as well as aiding target acquisition for you.
IMO, the next thing to buy after the weapon as described is lots of ammo, starting with light skeet loads. Even a 20 gauge recoils pretty hard for a tyro.As for ammo, I HIGHLY recommend testing different brands for tight patterns. Forget about spread,what you want is a single big hole,center mass. Chokes can or should be tight, stray pellets end up where they're not wanted.And,at HD ranges, the shells could contain breath mints and still be effective.I'd go with #3 buck in a 20,tho.
Also, for shooter comfort,especially for barrel cheasted men and ,uh, buxom women, sand off the toe of the recoil pad a little to stop it digging into chest muscles or tender tissues.
Hope this helps....