I'm a believer in .410 for home defense, provided it's buckshot and delivered from a barrel no less than 18".
That being said, if she's that small, why not go the handgun route? Many options, plenty viable, in some ways superior for home defense.
As for lights, are your night lights battery or solar powered? I wasn't into gun lights on the logic that I keep low ambient lighting through my house at night. Then I spent almost a week over the summer without electricity. Changed my way of thinking.
If you're insistent on a .410 shotgun, I'll echo what others have said: forget the pistol grip.
Get an 18" Mossberg 500 in .410 and put a bantam stock on it.