At Gatsby's party, the girls in yellow, Lucille got her dress ripped and because of this Gatsby got her a new dress.
Step-by-step explanation:
In the chapter, "The Great Gatsby", a party has been organised. In this party, all the people who are rich, famous and are their friends are invited and are a part of this party. The party was well organised and had things like oranges, lemon, Rolls Royce and so on.
At the party, "girl in yellow", Lucille ripped off her dress. But Gatsby being a good host and a considerate boy, sent a dress to that girl. This action was interpreted as a very sweet gesture by the girl and it was shown that he had a very helpful nature. According to me also, it is a very nice gesture and it made the girl comfortable again. It was very chivalrous on his part to do such a thing for the girl.