Poltergeist: The Legacy (1996)

Season 2: Episode 14

Kat and some of her friends experiment with an Isis board and manage to summon a presence of some kind or other. Kat collapses but is fine the next morning. She doesn't talk much about what happened and keeps quite about what they were really doing, afraid of getting herself and her friends into trouble. Later the presence forms itself as a woman who appears inside or outside their rooms and sings lullabies to them. The ghost seems to be passive, that is until one of the girls disappears overnight!