Right thing to do is gazump her. Do it now

Tell the police and the local authority that this is the most important week of the year in terms of revenue and the law is made to protect both licensees and other shop owners, and ~

A balance needs to be stuck in terms of give and take and continued complaints from next door are now being view as harassment against herself as a reasonable licensee and her customers, who are seeking legitimate enjoyment at a noise level which is not inconsistent with such activities.

Then see what happens!!