Is it permissible for the wife to use her stepdaughter's money for her personal needs, and is it permissible to spend the pension shared by the daughters with their father on the family?

If the daughter is an adult and of sound judgment, there is no harm in benefiting from the money she has willingly given. However, if she gave her money as a trust (wadī'ah), or if she was not an adult and of sound judgment, you are not entitled to benefit from it, even if the father agrees; because he is not permitted to gift the money of his minor children.

Regarding the pension disbursed to daughters, there is no objection to spending it on their expenses if they are poor; because the father is not obligated to spend on wealthy children.

If the husband spends on you from his daughters' pension (as a specific grant for them), and if he is in need of that, there is no objection to it, in accordance with what is customary. However, if he is not in need, the father is not permitted to dispose of the money of his minor or foolish daughter except for her benefit. It is permissible to dispose of the money of an adult daughter of sound judgment with her consent.