The girls' mimicry during the last part of Act III confuse Mary on a couple of levels. The first is the most evident in terms of them "making fun" or mocking what Mary says during her testimony. The actual act of them repeating what she says in high pitched voices and in unison is confusing to Mary, who already is not in sound state. The other reason why Mary is confused is that she is experiencing what it means to be an outsider. She has been on the "inside" for so long with the girls, and been in the position of power in Salem regarding her own roles in the trial and her own function as a part of the accusing group that to be on the outside so quickly is staggering. Mary had not experienced what it is like to catch Abigail's wrath and she learns extremely quickly. The girls' mimicry is a representation of how their clique can be a brutal one. It is a representation of how they can quickly close ranks and make someone who was once an insider an outsider in lightning speed. The girls' action confuse Mary because of this element in terms of what it means to be an outsider, a condition that Mary herself has not experienced. It is in this where Mary becomes confused and overwhelmed, perfectly aligned for recanting her confession and accusing Proctor, as Abigail would wish.