I'm not seeing that Elisabeth employed the phrase as a title, given that this is the only time in Scripture it is employed. Rather, Elisabeth, moved by the Spirit, refers to Mary as "the mother of our Lord" as a descriptor, no doubt to provide objective confirmation to Mary that she wasn't crazy and was indeed the mother of the Messiah King--which she was, just as David was His father.
Again, the problem is the implication that Mary is the mother of the totality of God, which would indeed place her in authority over Him. It needs to be emphasized that He is her Creator, God, and Lord first.
I never heard of this "justification". The justification I am familiar with is the Marriage at Cana story.
That's the usual example given, but the justification is the one I've heard repeatedly from Catholic friends and associates, both in RL and on the Web.
The issue is with your post 2,577 where you speculate that to a Jew motherhood is lordship. Unless Elisabeth was facetious, title shmitle, she did not exhibit such attitude.
but the justification is the one I've heard repeatedly from Catholic friends and associates
Either they are wrong yor you heard wrong. Mary is asked for her intercession, not to order Christ around.