מלכים ב, פרק ח׳, פסוק י״ח

Political friendships and military alliances between the Kingdom of Judah and the Kingdom of Israel eventually paved the way for a marriage that brought severe negative consequences to the leadership in Jerusalem. The roots of this situation lay in the close bond between Jehoshaphat and Ahab, the king of Israel. The two leaders fought side by side in battle, and this growing closeness ultimately led them to unite their families through the marriage of their children [ביאור שטיינזלץ].

As a direct result of this union, the king of Judah abandoned his own heritage and instead adopted the practices of the kings of Israel. The root cause of this spiritual corruption was his wife, the daughter of Ahab. Just as the royal house of Ahab had previously been led into sin through the incitement of Jezebel, the king of Judah was similarly pushed to do evil in the eyes of God by the influence of his own wife [חומת אנך].

While she is referred to elsewhere as the daughter of Omri, she was indeed the daughter of Ahab. The narrative simply alternates between identifying her by her father and by her grandfather [רלב״ג].