THE Bennets were engaged to dine with the Lucases, and again during the chief of the day, was Miss Lucas so kind as to listen to Mr. Collins. Elizabeth took an opportunity of thanking her. "It keeps him in good humour," said she, "and I am more obliged to you than I can express." Charlotte assured her friend of her satisfaction in being useful, and that it amply repaid her for the little sacrifice of her time. This was very amiable, but Charlotte's kindness extended farther than Elizabeth had any conception of; -- its object was nothing less than to secure her from any return of Mr. Collins's addresses, by engaging them towards herself. Such was Miss Lucas's scheme; and appearances were so favourable that when they parted at night, she would have felt almost sure of success if he had not been to leave Hertfordshire so very soon.

请教老师：

1）repaid her for the little sacrifice of her time. 这里的for怎么理解？

2）in being useful 怎么分析，其中being如何理解？可以说成in her being useful 认为是动名词词组，her是动名词的逻辑主语吗？

3）extended farther than Elizabeth had any conception of：这个比较句理解上有些不解，麻烦老师分析一下，其中of的宾语呢？这个of可否省略？尤其是没搞懂什么和什么在比较？

4）这里的them指代的是什么？