Moira Brandon was the previous owner of the compound that would later be used by the West Coast Avengers as their base of operations. When Hawkeye and his wife Mockingbird came to visit the mansion in order to check it out, they were attacked by the villain Crossfire, and the two heroes were at the villain's mercy. Moira Brandon ended up saving them when she used Crossfire's crossbow against him, but collapsed afterwards. In her final moments, Hawkeye made her an honorary Avenger.
Moira Brandon herself was an aging movie-star that had always lived an uneventful life. Her daring rescue of the hero couple cemented, that in the end, she herself was a hero as well.