I heard that the Virgin Mary visited this woman in 1917 and told her three secrets about the earth. She told the woman 9 days before these people died you have to tell them. Is it true that 9 days before the woman dies does she have something very important to tell the world?
I don't know if this woman has something very important to tell the world. I do know that whatever it is, it isn't from God. There are several reasons.
The Logical Reason: If it was something that God thought was important for us to know, why would he tell one woman, and have her keep it a secret? If God thinks it important then he would already have told us.
The Wrong Source Reason: Mary, the mother of Jesus, (who probably ceased being a virgin some time after Jesus was born) was a human person. Once she died she lost the ability to initiate conversation with people on earth. There are only two instances I know of when a dead person communicated with living people. One was Samuel who was called by the witch of Endor (1 Samuel 28), but she was surprised that the sťance actually worked. The other was Jesus, when he appeared to Paul on the road to Damascus (Acts 9). But Jesus is a special case, because of his divinity. After all, he spoke to many people on earth after his physical resurrection. Being the Son of God, he had the power to communicate directly with Paul, even when others couldn't. So anyone who claims that Mary told them anything must explain why she was given an exception, when it would have been simpler to let Jesus do the talking.
The "We already know what we need to know" Reason: "According as his divine power hath given unto us all things that pertain unto life and godliness, through the knowledge of him that hath called us to glory and virtue: Whereby are given unto us exceeding great and precious promises: that by these ye might be partakers of the divine nature, having escaped the corruption that is in the world through lust." (2 Peter 1:3-4) There is nothing she could tell us that God hasn't already revealed.