"Just because I a surrendering and taking my chances with the authorities, it doesn't mean I have to help you. Prison is better than the graveyard." It is fairly clear that her belligerence is going to continue. So, Amien uses the butt of his glaive to knock her and the others out. Each of you take a prisoner and tie them up, binding their hands and feet. Galandra notices that Amien was far too gentle with Siren, and reties her knots, as well as gagging her. Searching her, Galandra finds two wands, a jeweled broach and a fancy set of lock picks.
Finally lashing the unconscious bodies to the makeshift tower's poles, you think they may be secure for the moment.
Climbing the ladder, Galandra finds it is simply a couple shiny plates of silver and a tipped pot with a fire cooking in it. The entire assembly is on a swivel so it can be turned. Dismantling it takes just a few moments.
Looking to the north, the real lighthouse is about a thousand feet off across the sand.