Jesus-"You will know a tree by its fruit."
If we want to use conversion as a measuring tool, we would have to say Islam is correct which is the fastest growing religion.
But weren't they blessed? They became Christians. In doing so, they were baptized. Adult baptism requires repentance and belief. With this miraculous event, God, working through Mary, established the divine nature of His Church, so much so that millions of pagans were led into Christ's Church.
If people followed her advise, they were not converted because there is no call for repentence and asking God for forgiveness as required in scripture.
But in entering the Church through baptism, they repented of their sins and professed belief in Christ.
God uses all things to His glory so it is entirely possible that some of these people understood the message and "saw the light" so to speak. But, based upon what Juan told everone, this is not the gospel message.
Why would Mary be limited to strictly speaking the gospel message? She led the pagans to Christ's Church, and Christ Himself, as the woman whose offspring "crushed the head of the serpent."