The exact quote from Act I is:
"Let either of you beathe a wod, o the edge of a wodrd, about the other things, and I will come to you in the black of some terrible nigt and I will bring a pointy reckoning that will shudder you."
This is clearly a threat of physical harm on the part of Abigail towards the other girls. She establishes her control over the girls in this scene and insists that they resonate her claims that they only danced.
Abigail threatens the other girls by declaring she will bring to them "a pointy reckoning," suggesting great harm, maybe even implying that she will stab anyone who tells the truth. Then she describes how she witnessed the murder of her parents by marauding Indians so she easily convinces the others she is capable of violence.
Abigail is a forceful character who is basically evil. She has no status in the community as a single woman, who apparently, as everyone knows, had an affair with John Proctor. However she is able to influence and control the behavior of the other girls, like Mercy Lewis and Mary Warren.
Abigail's accusations of witchcraft give her power in the court, she is seen to be aligned with good, in league with God, pointing out those who are working with the devil.
If anyone dares cross her and attempt to deflate her power, she will turn her smart, wily behavior on them, accusing anyone of witchcraft just to remain the center of attention.
Abigail could easily turn on Mary or Mercy if either of the girls tried to tell the truth. She would put her considerable talents at performing to good use pretending to be possessed by spirits that are sent forth by anyone she chooses to name.
Abigail is very dangerous because of the power that has been invested in her by the court.
"Her accusations initially reveal a mischievous enjoyment in wielding power over other people's lives."
"She is at once a frightening and pitiable character, malicious in her accusations and sad in her need for close human contact and attention."