I know it is breed dependent and individual dependent, but what can you do to assist with broodiness.
I think one is leaving eggs in the nest, and rotating them so they do not go bad until one of misses decides to take up the task. I assume fake eggs or golf balls would do the same trick.
What about isolating the hen with some eggs and an comfy nest. The lack of friends might encourage her to make some new friends.
None of my hens have ever gone broody. I have only had 4 for 2 years and another 5 are less than a year old.