Man, fallout 4 is lame about reverse pickpocketing armor.
In short, it seems you can't. BUT there seems to be a reward for doing so?
I stole Glory's railroad armored clothes Mk I (the mark will be important later). it took a while cause I had a 21% chance to succeed). Then I replaced it with an armored red dress, and left her with her military fatigues, some 0 def clothes she was also carrying but not wearing.
Went out, waited 24 hours, came back, and she is wearing the fatigues! which have much lower defense than the armored red dress. So I stole the fatigues too, went out, waited another 24 hours, came back.
She is now wearing another Railroad armor, but this time Mk III! She never even tried the dress I gave her
But the weird part is that the game upgraded her clothes????
On the other hand, I stole her minigun and replaced it with Ashmaker, and she is now wielding Ashmaker. It's lame it only works with weapons.
edit: I tried with Desdemona, and she just gets some new fatigues identical to the old ones, so I don't know why Glory gets an upgrade.