Ansel and Winona's wedding had been planned weeks prior, even before the Heat Wave. They had been planning for a while so—considering their productivity—a week was more than enough time to actually execute the event.
However, at some point, Winona's grandmother found out about it and had been trying to insert herself for a while.
She had been camping in the organizer's office during working hours, critiquing or trying to modify whatever she found unsatisfactory. There were only a few days left before the event itself, and most of the things had already been settled, with them scheduling the venue for decoration the next day!
At first, they let her in because she claimed to be the bride's grandmother. She was so insistent that they did not have the time to tell the bride and groom before she was already inside!