Is it permissible for the spouses to meet, be in legitimate seclusion, and live together as long as the dispute case is still pending in court, knowing that the wife cannot withdraw the lawsuit at the present time?

If a woman has been lawfully contracted to you with the permission of her guardian and witnesses, then she is your wife. Her claim for divorce or khul' does not affect the contract unless the divorce or khul' actually occurs. Everything permissible for a husband with his wife becomes permissible for you with her. Even if you have not consummated the marriage, and custom dictates delaying consummation, it is preferable to observe that custom. We advise the sister to convince her family to withdraw the lawsuit and reconcile with her husband, for reconciliation is best. If you need the intervention of wise family members to establish foundations for reconciliation, that is better than resorting to the judiciary. If none of that is possible, then the judiciary is what will resolve the dispute.