Zinnia (Also known as Zach the Ripper) is a female afterlight that crossed during the civil war. She is known for having the power of an ecto-ripper (being able to "rip" objects from the real world into everlost, or from everlost to the living world.) She has a snappy personality, and enjoys war and all the weapons involved. In the American Civil War, she fought for the confederates, disguising herself as a boy. In a successful attempt to ecto-rip Mary into the living world, she was pulled into the portal as well, thus becoming a girl.
Neal Shusterman wrote her an out-of-book ending on his blog as well.