Is a woman's taking money from her husband's wealth without his knowledge, as compensation for her marriage to an older man, considered theft, and how can she repent and return the money when the husband has passed away and she has spent most of it?

If a husband does not fulfill the rights of his wife and children, she is permitted to take from his wealth, within reasonable limits, what suffices them. Otherwise, it is unlawful for her to take anything from his wealth. What she has taken would be considered theft and a breach of trust, and she must repent and return the money to the heirs or seek their forgiveness. This is based on the Prophet's (peace be upon him) saying: "The hand is responsible for what it takes until it returns it," and his (peace be upon him) saying: "Whoever has wronged his brother concerning his honor or anything else, let him seek his forgiveness today before there will be no dinar or dirham."