The correct phrase should be "oughtn't have spoken", which expresses regret or criticism about a past action. Oughtn't" (Option C) is the contraction of "ought not," which is used to indicate that something was wrong or inappropriate.

While "shouldn't" expresses a general prohibition or advice against an action, "oughtn't" conveys a sense of obligation. It signifies that it is required of her not to have spoken so rudely to her mother.