What threat does Abigail make to the other girls?

The episode of dancing in the woods, with Tituba, is highlighted with the conjuring of spirits, the illicit behavior of Mercy Lewis, who danced naked, and Abigail Williams drinking blood as a charm to get John Proctor away from his wife, namely by wishing Elizabeth Proctor dead.

After they are caught by Reverend Parris, and his daughter Betty, along with Ruth Putnam, are sick in mysterious ways the next morning, Abigail becomes very anxious about anyone finding out about what the girls actually did in the woods.  She knows that they will be punished for their behavior it is against the Puritan code of behavior to do such things.  She also knows that she, alone, is guilty of a more serious charge, the drinking of blood qualifies as witchcraft.

The other girls get very frightened when Reverend Parris becomes so upset about Betty's illness that he sends for Reverend Hale of Beverly who is an authority on witchcraft and bewitching of people. 

Betty, lying in her bed still and with her eyes closed, won't wake up because she is too frightened to face her father's punishment.  Abigail becomes frantic that some of the girls will tell in an effort to save themselves from being serverely punished.

Abigail comes up with a plan, she threatens the girls, to make sure that they don't confess to their parents or Reverend Parris what actually went on in the woods.  She wants them to say that they were only dancing, nothing else.  She is determined to make them listen to her, she is a forceful personality.  She makes it clear that she is capable of harming them, if anyone told the truth, she would come to them in the night with a sharp, pointy object and kill them.  She tells them that she means what she says, because she saw her parents murdered right in front of her.

Addressing the girls, Abigail makes the following threat:

"Let either of you breathe a word, or the edge of a word, about the other things, and I will come to you in the black of some terrible night and I will bring a pointy reckoning that will shudder you."  (Miller)

She wants to make sure that she has full authority over the girls and that they won't utter a word of the truth to anyone. Her final comments are:

"I have seen some reddish work done at night, and I can make you wish you had never seen the sun go down." (Miller)