Is the husband sinful for not informing his wife’s father of her request for divorce, given that she sleeps in another room after their disagreement over her frequent outings?

You bear no sin for not informing your wife's father of her request for divorce. It is advisable not to rush into granting her a divorce. Instead, strive to reconcile with her by explaining the obligation of obeying the husband, the impermissibility of leaving his house without necessity, that the husband's right is greater than that of the parents, and that requesting a divorce without a valid reason is forbidden by religious law and carries a severe warning. If she retracts her request for divorce and acknowledges your right, then forgive her and treat her kindly. If she does not retract, then let some righteous people mediate between you for reconciliation, if possible.