Andrea had been driving her little sister, Amy, back to school when the zombie apocalypse occurred. They were saved by Dale and have lived with him since then, and don't know what happened to their parents.
Andrea had to shoot her sister in the head after he was killed by the zombies and resurrected. She carries the guilt of shooting her sister, and feeling like she had been a bad sister before the apocalypse with her, and if it weren't for Dale, she would have committed suicide by staying in the CDC when it was about to explode.
You walk outside, you risk your life. You take a drink of water, you risk your life. Nowadays you breath and you risk your life. You don’t have a choice. The only thing you can choose is what you’re risking it for.Hershel
When you care about people, getting hurt is kind of a part of the package.Beth