They're attracted to the one thing about her that is different from themselves: her life force. It is very strong. It gives off its own illumination.
17 seconds sound clip from the Poltergeist (1982) movie soundboard.
You can hear this line at 01:18:48 in the Blu-ray version of the movie.
Quote context
[...]
- Would you all come on in? Gather round.
- There is no death. It is only a transition to a different sphere of consciousness.
- They linger in a perpetual dream state, a nightmare from which they cannot awake.
[...]