Question about Emma

That's the point and mystery behind Jane Doe. She is moved and/or happened upon'd, where which she exacts her 'revenge' on the people that cross her patch.

The GF was asked to come back later (two hours or so) by the son, so they could catch a mid-night film. [spoiler]That being said, once she left, I knew she'd be died later in the film.[/spoiler]

Emma never actually showed up, hence she didn't die. Her death was just another hallucination. If you notice, not counting Jane Doe, they only take out two body bags at the end (for Austin and his father). If you watch Austin's final scenes carefully, his shirt is covered in Emma's blood right up until he falls. As soon as he's dead, his shirt is completely dry, showing that none of the blood was real because Emma was never really there.