Jesus is God, God is Mary creator. Jesus exist before Mary, How then Mary mother of God. Did your mother exist before you?
You're right that Mary was Jesus' mother, and that God created her along with the rest of the humans. BUT Jesus did NOT exist before Mary did. Jesus was God in human form, thus Jesus only existed after he was immaculately conceived..
and btw, yes my mother DID exist before I was born..lol..