Is it permissible for a woman whose household does not provide for her to take from their money without their knowledge to spend on herself?

The maintenance of a married woman is obligatory upon her husband. If the husband does not provide for his wife adequately, she is permitted to take from his money without his knowledge what suffices her and her child, based on the Prophet, peace and blessings be upon him, saying to Hind bint Utbah: "Take what suffices you and your child in a reasonable manner."

As for taking from the money of the husband's family, this is not permissible, because it is a breach of trust.