What is the ruling regarding a girl marrying a man without the knowledge of her guardian, then marrying another man with a guardian and two witnesses after her dispute with the first and her saying to him: "Consider me divorced from you"?

Both marriages are invalid. As for the first, it is due to the absence of a guardian (wali), based on the Prophet's (peace be upon him) saying: "There is no marriage except with a guardian," and his saying: "A woman should not give another woman in marriage, nor should she marry herself off," and his saying: "Any woman who marries without the permission of her guardian, her marriage is invalid." As for the second, it is due to the invalidity of the first marriage, which created a semblance of a contract. Therefore, it is not permissible for her to marry another man until the first husband divorces her or the marriage is annulled. The woman's statement, "I consider myself divorced from you," is of no avail, because divorce is in the hand of the man, not the woman.