Complex sentence: The ghost children warn her that even if Coraline wins, the Other Mother will not let them go, so Coraline tricks the Other Mother by announcing that she knows her parents are hidden in the passageway between the worlds.
Split into simpler sentences: The ghost children warn her that even if Coraline wins, the Other Mother will not let them go. So Coraline tricks the Other Mother: she announces that she knows her parents are hidden in the passageway between the worlds.