You do know her, but not very well.
Here's a briefing of her backstory: Silence is a mute ex-thief. She was kidnapped from the Fire Tech Factory (though she isn't an Emberlin) by a gang of Aethasian thieves and eventually became one of them, until I scared her, causing her to fall through a roof. You carried her back to my metal crate, but that's about all you've seen of her. She likes to stay hidden in the shadows.