It is in this chapter that Jordan relates to Nick the past of Daisy and Tom and Gatbsy, and how this love triangle apparently resolved itself with the marriage of Tom and Daisy. However, Jordan remembers on the eve of Daisy's marriage finding Daisy drunk and clutching a letter. It is then that she drunkenly slurs that the marriage is over. Although we are not told, we can assume that the letter was from Gatsby. However, once she had been sobered up, she carried on with the original plan and was married after all:
But she didn't say another word. We gate her spirits of ammonia and put ice on her forehead and hooked her back into her dress, and half an hour later, when we walked out of the room, the pearls were around her neck and the incident was over. Next day at five o'clock she married Tom Buchanan without so much as a shiver, and started off on a three months' trip to the South Seas.
So, presumably, we can infer that having expressed her feelings and love for Gatsby with her drunkenness, she has managed to "get it out of her system," and is able to carry on with the original plan, which was of course to marry someone who was more her social equal than Gatsby.