Abigail did, right after Tituba 'confessed' to speaking with the Devil. She felt that Tituba was getting too much attention (after uh, literally accusing her of being buddy-buddy with Satan) so she wanted to cash in on the whole thing and fake confessed as well. Also, because they seemed to forgive Tituba for resisting the Devil, Abigail might have seen this as a means to eliminate the people she didn't like (cough cough Elizabeth Proctor) through the Salem witch trials.