This is like my method. I have Wyandotte bantams that are persistently broody all summer. At the 1st sign they go in the small prefab coop. The change of living arrangements & denial of access to their nesting box of choice usually does the trick. Unfortunately they do tend to go broody again fairly quickly but @ least this way they aren't losing tons of weight, have room to exercise & bok away to their hearts content & they aren't driving the rest of the girls crazy.Good to hear! Hopefully you can break her. All good advice. Dunking in cold water can help.
We’ve had a broody we accidentally broke! we were getting chicks, she had been broody a couple of weeks, so we moved her to the brooder with a nest. We didn’t think to cover the wire top to keep the light low in there (covering half of the top where nest is located). So, the new location in brighter light, away from the flock broke that chicken pretty quickly - much to our disappointment.
recently, we’ve had a couple go intense broody. We don’t need a broody, so we take them to a separate pen, in sight of the run, but not next to it, not adjoining. We give them fresh food and water, with yummy seed filled scratch that even a broody has a hard time resisting. Usually they eat and drink and perk up. They go back to the coop at night, with nest boxes closed off. So far, a few days in the separate pen during the day, with fresh tempting food has helped the broodies snap out of it. They are not with their flock, but want to be. They are eating and drinking more than when they sit, so have more energy, they do not have a nest. So, it is several factors that act together to push them back to normalcy. Yours seems to be very stubborn, so hopefully you can get her back to normal health and activity!