Following the deaths of her two eldest brothers, and the warding of her sole survivIng brother at Winterfell, Asha was the last child of Balon Greyjoy left to him, and he effectively raised her as his heir. Asha reaved, raided, and fought the rest of her people, captaining a longship and winning the regard of her crew.
The War of the Five Kings
During the Ironborn Invasion of the North, she took Deepwood Motte from House Glover, as per her father's orders. She is unsurprised when she discovers her brother fled Pyke for the Starks - accounting him as too green for the Isles, anyway. When word arrives of Balon's death, Asha abandons her conquests to return home and claim the throne of her father by participating in the Kingsmoot.
Her attempts to become the new sovereign of the Isles are thwarted when the Ironborn name Euron Crow's Eye their new liege. Asha flees to Ten Towers, to reside with her kin the Harlaws, while Euron ends the Invasion of the North, choosing instead to invade the Reach. He launches an attack on the Shield Isles, pulling much of his strength away from Pyke and the Iron Islands.
Asha and Rodrik the Reader, remaining behind in Ten Towers, set to work on undermining their new liege. Though Asha is married to Erik Ironmaker, the eight and eighty year old Lord soon dies under suspicious circumstances. Rodrik arranges her a second marriage to Gran Goodbrother - thereby tying the three most powerful houses in the Isles together, firmly against Lord Euron.
When the Crow's Eye sends word home, demanding reinforcments following his defeat at the mouth of the Whispering Sound, the Ironborn send none. Between the workings of Asha, Rodrik, and Aeron's own independent proselytizing, the defeat at sea proved the final nail in Euron's rule. The Ironborn sent no more ships, and not long afterward Euron was defeated and slain in the Battle of the Shields.
The survivors raced home, bringing tales of the Redwyne fleet they thought would be following them. Asha stepped in, claiming the Seastone Chair for herself, and this time no one - not even her uncle Victarion - resisted.
Asha Greyjoy set about preparing the Isles for the Redwyne attack, but quickly realized there was little that could be done. Two major defeats at sea had cost them enormous numbers of ships and fighting men, and with winter approaching the Isles always half barren, there were no easy means of resupply. Desperate, Asha turned to the one source she knew might be able to stave off the vengeance of the South - she turned to her brother Theon, in the court of King Robb I Stark.
The Kraken and the Direwolf negotiated a deal - the Iron Islands would bend the knee to Winterfell, giving the Iron Islands the protection of three other kingdoms in the face of southern aggressions. The agreement also meant that the Ironborn could once again access the bounty of the mainland - with a long winter fast approaching, sustaining themselves after the loss of so many men would be difficult. It had the added bonus of granting the Ironborn the chance to raid the Reach and Westerlands with little repercussion, though the Starks have always expressly forbade such action.
With the deal signed, and Robb Stark treating with Renly Baratheon to end the war between the Reach and the Ironborn, Asha set about rebuilding her homeland. She worked tirelessly for many years, resetablishing their strength at sea with trees from the Wolfswood, and opening new mines on Great Wyk and Harlaw.
When the Ironborn had grown closer to their old strength, many petitioned Asha to rise against the Starks and seek their independence once again. This she declined, citing the benefits of trading with the North and how isolated they would be, should they abandon them. Asha had no delusions about the strength of the southern fleets. She had no desire to face them again so soon, and with her marriage to House Goodbrother and bloodties with House Harlaw, few of the Ironborn houses could dissent.