Once Amandine goes down it becomes a damage race. After her fourth Seduce > Nuke move she'll eat somebody and blow you all up. Since you don't have to worry about more adds, just knuckle up and burn her down, blowing all CDs.

A SMN makes this fight a ton easier, since they can use the lvl 2 LB on both the boss and the add, and their single target damage really grinds the boss down fast.