Is a girl, married or unmarried, obliged to spend on her family even if the father is well-off, or is she permitted to spend as she wishes, such as giving her mother a monthly allowance or spending on the house?

A girl is not obligated to financially support her parents if they have sufficient means. However, if she voluntarily gives them money, it is a good deed for which she will be rewarded, and through it, she will gain their contentment and love, as Allah Almighty says: "And whatever good you do, Allah is Knowing of it," and as the Prophet, peace and blessings be upon him, said: "Exchange gifts, and you will love each other."