Mary Poppins appears to humans as a kindly nanny. Despite her appearance she can fly and alter reality. She is revealed to be a manifestation of God when she confronts the Antichrist to prevent the Apocalypse, saving all mankind.
Connection to God
Mary Poppins appears to represent Shekhinah, Binah, or Sophia.
From readings of the Talmud, Shekhinah represents the feminine attributes of God. Shekhinah is sometimes represented as a goddess of wisdom. In this sense, Mary Poppins is the personification of Skekhinah.
Sophia is a neopagan goddess of wisdom, and like Shekhinah, she can be associated with the feminine attributes of God. Hagia Sophia represents an understanding of the Holy Spirit.
Binah is the second intellectual sephira on the kabbalistic Tree of Life. In occultism, Binah represents the womb. Binah gives birth to all of creation.
Mary Poppins is a personification of all these concepts, and as such, she represents the feminine side of God that cares for the welfare of mankind.
Mary Poppins reveals her godly status by informing the Antichrist that she is on "every page" of the Bible, whereas he is in "just the one book".
Battle with the Antichrist
In 2009, the Antichrist is found by Mina Murray , and Orlando in London. When Orlando uses Excalibur to send a signal to Prospero in the Blazing World, it is thought that Prospero communed with God to beg for the salvation of mankind. Thus the caring, motherly side of God, in the form of Mary Poppins, came down from the heavens to destroy the Antichrist. She did this by altering reality to transform the Antichrist into a chalk drawing. With the words "splish, splash", she summoned a rainfall to wash away the chalk drawing. She then flies back into the sky, presumably returning to Heaven or the Blazing World.