The IW force fields can be shutted down from her mental fatigue, now both Magneto and GL had plenty of ways to cause her huge mental fatigue:
Enhancing their physical strenght into the Class 100 Strenght level, punching the field around her until she collapse on the ground for the feedback then kill her.
Magneto can use light to pass through the field, and so can GL.
Magneto can jam her brain impulses.
Magneto can surround her face in a metal cage and then aument the pressure until her face is a jam of flesh and bones into a metal box.
Just to name a few chances
Also, someone here needs to read more about John Stewart, the guy was able to create a huge starship even equipped with small ships to use in case of emergency, and it takes a lot of will power, experience and mastery over the GL power to do it.
He can also do much of the Thing Maggy can do, but the battle will be tough anyway.
Hal Jordan will be tough too.Hal in bloodlust mode is a force to reckon with, we all saw what he do in Emeral Twilight, he destroyed most of the GL Corp top dogs, even his mentor, and Sinestro.
Back to Magneto support, he can detect the IW through the waves created from her movement then beat down her.