Abigail doesn't want to ruin her reputation so she warns the other girls that she would hurt them, and starts accusing others. She doesn't want to mention that the reason she was there at night was to find a way to kill Proctor's wife.
"Let either of you breathe a word, or the edge of a word, about the other things, and I will come to you "
Tituba wants to prove that she isn't a witch after Abigail accused her of compacting with the devil. So Parris and Hale assume she is a witch and Tituba says it is not true and they believe her. Although she confessed to witchcraft but says she is no witch
Mister Reverend, I do believe somebody else be witchin' these children