I agree Mary is trying to protect herself and not hurt Edmund. How successful she will be is questionable. I described Mary’s decision to ‘admit his [Edmund’s] attentions without any idea beyond immediate amusement’ as revenge because it is unfair to Edmund to admit his attentions if he has no chance of succeeding. Also I think Mary feels showing Edmund she is indifferent to his indifference is important to her pride which made me think of Maria: ‘her mind became cool enough to seek all the comfort that pride and self revenge could give’ (21). I admit neither reason meets the definition of ‘to extract punishment’ (dictionary.com). (:D)