Who was athaliah? why is she a significant figure in israel's story?

Athaliah was queen in Judah, and significant for being the only female monarch to rule by herself in Israel's history.

It is commonly assumed that Athaliah was a daughter of monarchs Ahab and Jezebel of the northern kingdom of Israel.  She was married to Jehoram, the ruler of the southern kingdom, Judah, to cement an alliance between the two kingdoms.  After Jehoram's death, his son Ahaziah became king and Athaliah was the queen mother.  Ahaziah ruled only one year before he was assassinated by Jehu of Israel.  Athaliah then took over the rule of Judah and ordered the execution of any others with a claim to the throne.  She ruled for six years before being toppled in a rebellion that brought a surviving grandson of Jehoram to the throne.