Abigail is looking for a scapegoat. When she names other people and attaches them to the actions that will earn them consequences, she diverts attention from herself. She repeatedly admits that she danced, but she dissociates herself with the idea of conjuring spirits, a much more serious crime.
Usually, a true friend would not turn on her friends and blatantly accuse them. This event which occurs near the beginning of the play demonstrates Abigail's true nature for audience members. The audience learns that Abigail cannot be trusted and that she is not loyal. This turns out to be a trend for Abigail for the remainder of the play. It also foreshadows her eventual naming of many others who conjure spirits. All of her accusations have no physical evidence so it is possible that she is lying. In fact, she could have been lying about Tituba and Ruth.