Is it permissible to supplicate for the reversal of a decree after performing Istikhara?

If the questioner has sought Allah's guidance (istikharah) concerning an matter, and it later becomes clear to her that it will not bring benefit or may harm her, then there is no objection to her supplicating Allah to avert it from her and to turn her heart away from it. Supplication repels divine decree (qada'), as mentioned in the hadith (definition): "Nothing repels divine decree except supplication." The "divine decree" here refers to the destined matter that the servant fears. If one is enabled to make supplication, Allah will ward it off from him.