Nothing really. At some point, she was mixed up with another women (in the Gospel of John), "the woman taken in adultery", and they are not the same person.

The Gospels aren't really historical documents and Mary Magdalene was probably not a real person. She's just there in the story to witness three important events: the crucifixion, burial and empty tomb of Jesus.

There are plenty of alternative theories about her role in Jesus' life, but generally not espoused by serious scholars. As part of fiction writer Dan Brown marketing of the novel the Da Vince Code, Brown claimed that Mary Magdalene married Jesus and had a child by him. That child was supposed to have living descendants, etc etc. You can watch a thorough debunking of this claim here: https://youtu.be/UAtoP5nFhh4