She'd have to start out in light form or else she'd get blitzed or a laser to the brain before she could react.
I see it more than likely that she'd be in light form considering the scenario. Really that's how she travels and considering 99% of all foes can't hurt her in that form….seems logical that she'd go against an unknown foe in this form.
She also is able to emit various energies, so it's safe to say that if she emits the energy of a Red Sun, Superman is nothing.
Because she somehow instantly knows SUperman's weakness and is able to turn into red sun energy?