First we meet Abigail Williams in the very beginning of the first act. She is described as seventeen years old girl, strikingly beautiful, an orphan. It is even hard to tell this girl is the antagonist of the whole play. She seems so innocent and trustworthy.
As soon as Abigail stays alone with the girls in the room we see what kind of person she really is. She threatens and intimidates the girls. In line 349, when Betty awakens and accuses Abigail, she smashes the child across the face and yells: "Shut it! Now shut it!". This shows us Abigail as a bad leader, evil character, which has an enormous control over the innocent girls.
There is also an internal conflict in Abigail's life. We meet John Proctor whom Abigail is in love with. He does not love her back, he is married and has children, but she still keeps believing Proctor will be hers. In line 471 she says: "You loved me, John Proctor, and whatever sin it is, you love me yet!" Everything she does is for the sake of love. Which is not an excuse at all, but now it makes more sense why she gets into trouble connected with witchcraft and involves the girls in it.
The further we read the play, the more we get to know Abigail's personality. She accuses everybody, but not herself. The only thought on her mind is how to get Proctor's love. She does not feel sorry for anybody. She accuses Elizabeth Proctor in witchcraft to get rid of her and have Proctor for herself. But this will never happen.
In the third act a big conflict in the court is shown. Abigail pretends she feels cold and sees a yellow bird. Abigail says in line 1001: "But God made my face; you cannot want to tear my face. Envy is a deadly sin, Mary!" This makes everybody think that an innocent girl Mary Warren has worship...