Other mistake: When everyone is looking for Bobby, Matthew Lillard says that it is no use shouting because the glass is 100% sound proof. Yet when he is trapped in the cage, he hears Maggie screaming directions for him to dodge the ghost - not sound proof at all then.
Other mistake: When Dennis jumps out from behind the glass wall shield, leaving Arthur behind it and The Hammer and Juggernaut ghosts attack, Arthur bangs the glass yelling as if he can't get out; but the wall shield is only propped up, unsupported and should've fallen straight forwards when he thudded his fists on it.
Other mistake: When Maggie puts the "magic" glasses for the first time, you can see that the light in the right (left to us) lens sparks and then turns off. In the next scene it works fine. (00:31:21)
Other mistake: In the scene where Cyrus's Nephew first sees the kids in the in the machine. (1:18:45) The shot goes back and forth from him to the machine. The first 2 time the glasses are fine the last shot (1:18:550 The prescription inserts in the glasses are crooked. Bad editing. (00:18:45 - 01:18:55)
Answer: She was a trapped soul in a house full of magical spells forcing her into a pivotal configuration. When it was destroyed, she was free. Like at the end of the movie, "Ghost," a bright light shined upon her to say goodbye to her loved ones.