Is the questioner considered sinful and the cause of her husband divorcing his first wife, knowing that the reason for the divorce was the first wife's slanders and false accusations against the questioner, and the discovery of her stealing her husband's money and practicing sorcery?

If a woman accuses you falsely of theft and adultery, this is a grave sin, as Allah the Almighty says: "Indeed, those who accuse chaste women, unaware [of evil], believing – are cursed in this world and the Hereafter, and for them is a great punishment."

However, you are not permitted to seek her divorce, as the Prophet, peace and blessings be upon him, forbade it by saying: "A woman should not ask for the divorce of her sister to empty her plate." You must repent for what you have done.

Furthermore, accusing someone of sorcery without proof is dangerous and impermissible; the default assumption for a Muslim is innocence, and Allah the Almighty has forbidden ill thoughts.