After talking to Luke in the back yard and receiving the chuppah, Lorelai rushes indoors and suddenly tells Rory to pack – they are going on a road trip. Rory points out that Lorelai and Max are supposed to be getting married the coming weekend, less than a week away.
To surely nobody’s surprise, Lorelai begins crying and says she can’t marry Max. The reason? Because she didn’t want to put on her wedding dress every night, as a besotted Emily did before marrying Richard. Clearly her mother’s story affected her deeply, much more so than she let on at the time. While Emily’s story made Sookie and Rory feel more loving toward their boyfriends, it demonstrated to Lorelai that she didn’t really love Max at all.
Rory instantly accepts Lorelai’s explanation without further discussion, and begins on the practicalities of packing. Her way of showing support is to not add further to Lorelai’s unhappiness by making her feel guilty, and to begin focusing on what Lorelai wants to do instead. If running away is Lorelai’s plan, then Rory will go along with it unquestioningly.
Although Lorelai has known for some weeks at least that her wedding to Max cannot take place, it was her mother who helped her crysallise the reasons for it (and the phone call to Christopher gave her further ammunition against Max).
However, it was Luke giving his blessing to the marriage and apologising to her for his behaviour towards Max that seems to have been the catalyst for her admitting she couldn’t get married. Lorelai was pushed into Max’s arms when Luke reunited with Rachel, and she seems to have got engaged partly to spite Luke when he tried to put her off the idea.
With Luke now backing down and saying he will support her as a friend, all the impetus seems to have been lost, and she has no reason to marry Max. Luke finally discovered the way to make Lorelai change her mind about marrying Max.