There is obviously no point in her sitting on unfertilised eggs. It is too late in the year to set turkey eggs if you want to eat the offspring at Christmas. But if you just want more turkeys then it's not too late. Turkeys usually lay through till early October so you might be able to source some. But turkey egg incubation period is 28 days so if she has been broody for a while already it is better to try and break her broodiness as she will lose condition.
Remove her from her nest site and put in her in an open but secure pen where she cannot get to her nest. Leave her in there 24/7 with food and water and you should find after about a week she will give up. Does she have other turkeys to keep her company or only chickens? It is better if turkeys can have at least one other turkey for company. It's also better to keep turkeys separate from chickens if you can to reduce the risk of blackhead, especially if you are rearing young turkeys, although mature turkeys cope rather better.