Ava grew up on the streets of Treviso from a young age. She doesn't remember her parents, they died when she was so young that she can't recall a time when she had the warmth of a mother or father. She was in a group of young kids that were taken into the Crows because they were orphans, no one would miss them if they didn't survive the training, but also, they knew the streets of Treviso well already. They could be used for certain things that the Crows needed done but couldn't do themselves.
She's always been stubborn, resilient to a fault, aggressive when needed and yet, still has a rebellious streak. It was no surprise when she became a full-fledged Crow, slightly young for it, but Viago believed in her, as much as he'd admit he doesn't. When she was given that contract, told that it was her first as a real Crow, she knew what that meant. If she fucked it up, there was a good chance she wasn't coming out of it alive.
She didn't expect Teia and Viago to stick their necks out for her. She's grateful to them even though she doesn't believe she's worth it. Ava knew what to expect, she'd heard things about the Antaam and knew there would be prisoners there. But hearing about it and seeing it are two different things. So her impulsiveness took over and she figured she could complete her contract and free some prisoners. Two birds, one stone, right?
She was so wrong.