You guys are missing something extremely important Planar Binding means she follows the charmed wizard not the gnome at all, and the sucubi controls the wizard via Dominate Person. Which means she can literally just get free and kill the gnome and wizard and run lose on the material plane you guys are massively overlooking two major details here. That's the person she has to listen to and the fact that person is already under her control Dm is playing you guys hard. She didn't even need to cast suggestion after dominate person as the order itself isn't what could kill the wizard.
