Most significant is the fact that John Proctor is put into jail. This is a blow to Abby, who in her heart, had desired to have him for her own from the very beginning. Bummer for her...
Also, the general feeling of the townspeople changed towards the girls. Where they used to think of Abigail as "a saint", the townsfolk are now, after all of the arrests and hangings, starting to rethink their initial good will. Part of this is caused because "the rumor here speaks of rebellion in Andover", which indicates that the people of the neighboring town of Andover have overthrown the courts. Danforth tries to deny it by saying "Andover is remedied. The court returns there on Friday" but Parris is not convinced. He thinks that Abby "had close knowledge of [Andover]" and that she was worried that rebellion would occur in Salem too, so she bolted. She knew that if the town turned against her, it would be bad news. Salem is in fact turning; Parris found a dagger stuck in his door, indicating there are ill feelings towards him and the courts. To add to this, the cows are wandering, fields are unplowed, and children are orphaned. All of these factors-John, Andover, the townspeople's feelings, and the devastation left in the wake of the trials, probably led Abby to get out of there before she was held accountable.
the proper response to a question of this magnitude is simple. Abigail felt wronged by mercy so in the following events decided to vacate the premises.