The correct option is E doesn't need to have much to say to her niece
The passage states that Lady Bertram struggles with writing to her acquaintances, here, her niece. It suggests that they do not converse much and that she doesn't have much to say to her. Therefore, option D is the correct answer. The statements of options A,B,C and E are incoherent with the tone of the text, and thus, are incorrect.