“She was a sinner like all of us, to be consistent in its doctrine in this area is a problem for your church.”
Hmmm, no. She IS the Mother of God. She committed no sin in her time on this earth. There is not problem with the Catholic teaching of this mystery. The problem lies with those who are ignorant; willingly or unwillingly so.
It is NO mystery it is an inconsistency in your church teaching.
Either Jesus was "the only one that could fulfill the law perfectly " as your catechism says or he was not.
Either they are wrong here or wrong when they say Mary was sinless.
If they are wrong in their Catechism how could that be if the Pope and Magastum under him are infallible ?
This is no problem for me, Jesus needed a human mother, He himself was God.