As there is no chance of her efforts having any positive outcome, it is in her best interest (from a health and a safety perspective) to get her over her broody state sooner rather than later so that she can return to normal eating/drinking/activity levels and will, once again, be using the coop for security.
A "broody buster" is simply a wire cage/dog kennel/etc that is used to get a broody hen to "snap out of it". The cage is placed in an elevated position (ie on cinder blocks) so that air flows up under neat it. There is no bedding used and the hen is confined in the cage for 2-3 days with food and water. The inability to "nest down" and the cooling effect of the air flow reaching her underside at all times will "break" her broodiness so that she returns to life as a non-broody hen.
Setting a clutch of eggs is very taxing to a hen - they stay on the nest 23+ hours a day eating and drinking little and holding waste for extended periods of time - leaving the nest only a couple of times per day to eliminate and grab a little food/water. This takes a toll on their body and when it is all going to be for naught since the eggs have no chance of hatching there is no sense in allowing that to happen.