Aggra is the captain of Draka's Fury which was destroyed near the Lost Isles. When the ship sank they lost their "precious cargo", which ended up being Thrall. She then appears as a quest giver on the Lost Isles.
In the book The Shattering, she teaches Thrall to become a better Shaman and, despite quarrels, becomes his mate.
It has also been confirmed by Chris Metzen. 
Aggra is a favorite of Greatmother Geyah, Thralls grandmother. She met Thrall during his quest to Nagrand to learn more about the elements from the Mag'har. Aggra, being furious at Thrall for, in her opinion, abandoning his people and homeland in favor of an alien land, begins to quarrel with him.
As Thrall begins his preparations for his vision quest, Aggra is assigned by Greatmother Geyah to be his mentor. Despite Thralls and Aggras relationship starting out with spiteful comments and arguements, eventually Aggra begins to fall in love with Thrall and his great heart. As Thrall gets ready to depart Nagrand to return to Azeroth, Aggra openly admits her interrest, and becomes his mate.
Aggra is exactly what a female orc is supposed to be: Strong, intelligent, and incredibly loyal to those she holds dearly. She is young, and yet a very powerful shaman, fit to teach Thrall, former warchief of the Horde, as he prepares for his vision quest.
Patches and hotfixes
- Patch 4.0.3 (15-Nov-2010): Added.