Is it permissible to dispose of something held in trust without the owner's permission, even with the ability to return it upon request?

If the woman grants you permission to manage her wealth, there is no sin upon you. If the woman dies, the wealth belongs to all her heirs, not solely to her daughter. This is because her request to give the money to her daughter after her death is considered a bequest to an heir, which is forbidden by Islamic law unless the heirs approve. It is advised to return the trust to the woman and inform her of the Islamic ruling. She may give her daughter whatever she wishes during her lifetime, provided there is fairness among her children or a legitimate Islamic reason for تخصيص (designation/special allocation). A bequest to the daughter after death is not enforceable except with the permission of the remaining heirs.