The broody hen now sits on another chicken like it's an egg.

[Judee]

I looked at some of the other broody hen threads, but still feel compelled to share my experience. My gray hen hen was broody. I got that. Put her in the dog kennel for awhile when other chickens weren't looking, but the other girls found the covered crate, anyway. She made a fuss, they made a fuss. I folded and figured she'd grow past it like others have done.
A smaller hen began crawling under her... and they'd stay that way all day and night for a month unless I pull them out of the coop. The first broody gets out, eats and drinks, then returns as though she's sitting on an egg. The smaller hen stays in the coop unless I force her out. The other girls have started picking on the smaller one (I can nearly hear them calling her "freak"!!) I tried caging the first broody. The younger one actually runs to me flailing and chirping, very upset. Augh. This is crazy. I guess I need to "jail" both of them? Might they die of broken hearts?

 

[All4Eggz]

Yes, jail both of them.
How old is the “younger hen”?

This is not good. She can suffocate. I’ve recently had 2 pullets suffocate because they sat on top of each other with some others pressed against them… no bueno.

 

[aart]

Put her in the dog kennel for awhile when other chickens weren't looking, but the other girls found the covered crate, anyway.

Why was the crate covered?
No problem with being in sight of the other birds.

 

[Judee]

Covered the side of the crate. The girls would come over to fuss, then the caged broody would fuss. when I tarped the side of the crate, they went on their way and she settled down.

 

[Judee]

Yes, jail both of them.
How old is the “younger hen”?

This is not good. She can suffocate. I’ve recently had 2 pullets suffocate because they sat on top of each other with some others pressed against them… no bueno.

 

[Judee]

The younger one...by a year. Yes, I was worried about her suffocating, but they seem to have adjusted a bit. Still, the younger one isn't eating enough. those plaintiff cries when they're separated....augh!

 

[rosemarythyme]

Covered the side of the crate. The girls would come over to fuss, then the caged broody would fuss. when I tarped the side of the crate, they went on their way and she settled down.

Generally better to let them see each other even if they're riled up about it - too long out of sight, out of mind and you might have a harder time returning the broody(ies) to the flock.

I'd cage both birds separately (or break one completely, then the other) as they'll probably cause issues if caged together at this point.