Random House 2nd Ed "auxiliary, subsidiary".
My Shorter OED is as you say but I note it doesn't even have "co-pilot".
SO instead of dealing with YOUR contention about "co-" you just seized on the meaning of co-pilot and went on with your other argument ... so you changed the subject before that last one was settled?
Amazing! No wonder we don't get anywhere! You guys view arguments like weapons or calibers or something. "Well that one didn't shut 'em up, let's try this one."
Let’s let everyone decide if any of these sound alright:
“Mary, our subordinate Redemptrix.”
“Mary, our subsidiary Redemptrix.”
“Mary, our assistant Redemptrix.”
“Mary, our joint-Redemptrix.”