Abstergo always made sure of knowing well their "subjects", and also those who could be integrated into their Animus program. Desmond Mileswas found and captured; Clay was betrayed by Lucy Stillman and disposed of. But they were not the only person who were targeted Abstergo.
Daniel Cross was a test subject highly instable because of something we call the Bleeding Effect. Without the use of an Animus machine, he could live his ancestors’ memories. Though those visions were not controlled nor desired, they helped him discover his past and ancestry.
But was Daniel unique? Or is it possible to find catalysts, objects or places that could trigger the ancestors’ memories into an individual's mind without prior exposure to the Animus ? Another possibility is that she heirs to a very special DNA. If “Sages” or people with strong Precursor DNA were present in her ancestors, it may be possible to trigger it.
In September 2013, as she was unknown to the Assassins or the Templars, Gabrielle witnessed some memories of an Ancestor, Peter Spizaetus, when walking into a key place of his life.
At that point, she came to understand that her grandfather, whom she thought was a boring old man, was an Assassin, and lived a life full of war and conflicts.
Joining the Assassins
After exploring the death of the Singer, she was found by Emilio was asked to protect her. Audrey joined the team, and helped her live the memory of Peter being captured and tortured by the Templars.
They were trying to find the Apple of Eden #4, lost since 1945.
Personality and skills
Gabrielle is a curious woman, dedicated to find the memory of her grandfather, who she came to deeply respect the life he had lived.