Sounds like a good plan.
You will also have to remove all the bedding from the coop and nest boxes and burn it.
Don't use straw as its hollow stems provide great hiding places for mites. Fresh sand or soft wood shavings are much better.
Use a blow torch on the undersides of the roosting bars mornings and in the evenings before the birds go to roost.
Stick double-sided adhesive tape on the underside of the roosting bars and ends where they meet the wall so any mite on its way to feed on the chickens will get stuck to the tape.
Check the other broody and her eggs each day for mites.
To be on the safe side, I would remove her old nesting material when she gets up to relieve herself and eat etc.
Prepare a fresh one using new nesting materials and put her eggs back in.
Use mite spray all around her new nest so the parasites cannot get to her.
Fingers crossed that your hen will survive.