Abigail is clearly a young woman of great charisma and strength, as is seen in Act 1. She knows what is at stake now that her Uncle, Parris, has seen a group of girls dancing naked in the woods and that it could mean whipping or worse for her. We see Abigail's desperation but also her implacable strength of character that forces the girls to bow to her commands. Note how in Act 1 she "furiously shakes" Betty to get some kind of response from her. It is when Betty shouts out what Abigail did that we see Abigail's true colours:
You drank a charm to kill John Proctor's wife! You drank a charm to kill Goody Proctor!
At this point Abigail "smashes her across the face", screaming "Shut it! Now shut it!" She quickly works to assure everyone of the "truth" to try and limit their punishment:
Now look you. All of you. We danced. And Tituba conjured Ruth Putnam's dead sisters. And that is all. And mark this. 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. And you know I can do it; I saw Indians smash my dear parents' heads on the pillow next to mine, and I have seen some reddish work done at night, and I can make you wish you had never seen the sun go down!
This, then, clearly shows how Abigail maintains her control of the girls - it is through intimidation - physical, mental and psychological, which induces terror in the girls and makes them compliant to her commands. Note how in the rest of the play the girls always follow Abigail's lead and never gainsay her.
One simple word explains how Abigail controls the rest of the girls in Arthur Miller's The Crucible--fear. The girls are afraid of her, and probably for good reason. Two specific incidents support this idea. The first happens early in Act I, in Betty's bedroom. All the girls are clearly playacting and in some ways--for Betty it's literal--paralyzed by fear. They've overstepped the boundaries in several ways, not the least of which was dabbling in witchcraft in the forest the previous night. When the girls seem concerned that someone, probably Mary, is going to tell, Abigail goes on a tirade, threatening to kill them and invoking the bloody scene of her parents being savaged by Indians. That put plenty of fear in the girls.
The second episode is when Mary Warren does finally tell the truth in court, attempting to expose the girls' fraud. Instead, Abigail manages to turn it all back on Mary, taunting her and frightening her so badly that Mary ends up turning her accusations on her employer, John Proctor. This fear and intimidation which Abigail wields is powerful--powerful enough to cost more than twenty people their lives.