Final answer:
Anne is worried about hurting Margot's feelings because Margot's silence and faintly mocking smile indicate that she is upset. Anne wants to maintain her relationship with Margot, and she doesn't want anything to come between them.
Step-by-step explanation:
In the given excerpt, Anne is worried about hurting Margot's feelings because Margot's silence and faintly mocking smile indicate that she is upset. Anne's burned hair and her uncle's hurt and faintly hostile tone suggest that Anne's appearance may have disappointed or upset Margot. Moreover, Anne wants to maintain her relationship with Margot, and she doesn't want anything to come between them.