I'm trying to get Old Lady Gibson's unique Sawed-Off Shotgun without killing her, but she won't use any other weapon I've tried giving her. I'll happily leave her the caps for the blasted thing if only she'll use a Minigun or something instead. Has anybody had any luck with some other weapon?
Maybe I'll go buy her a Gauss Rifle...
The gun can be reversed pickpocked, first you need to take away the bullets she has for the gun.
Second, give her a weapon and also the bullets for that weapon you are "giving" to her.
Walk out to another area then return.
Pick the desired weapon from her.
Good luck.