I don't care what church you go to, that statement is BLASPHEMY !!!
God has no 'mother' and to say that he does constitutes polytheism, and clearly mocks the first commandment.
My G-d is bigger than your G-d. He can knock the stuffing out of your G-d. Not only that but he makes more money.
Actually in one sense you are wrong. God is 3 persons and Jesus is one of those persons, and Marry is Jesus's mother. Hence it is accurate to call Marry the Mother of God. I am not a Catholic following person, and I have my problems with certain catholic ideas such as praying to Marry. But I have no problem with the statement that Marry is the mother of God. Since she is the mother of Jesus who is one person of the trinity.