If I had only heard normal hens' egg songs, I wouldn't be saying this, but...
We had two extreme singers. After many years keeping many different breeds of chickens.
The batty ones were Cream Legbars, although I've heard of several breeds doing it.
They would sing extra loud for hours. They would start up singing again every time another hen laid an egg, even when the actual layer made minimal noise. It was an all-morning affair. It was driving me bonkers.
Roosters crowing don't bother me, and I've never paid much attention to a typical hen singing. So, at first my mom didn't believe it was really an issue. Her hearing is... not great.
Then we figured out that her bathroom insulates her room from chicken noises, but my room has no such luxury. Even my office area is much louder.
Acoustics can be weird that way. The topography of land and exterior shape of buildings / internal layout / materials used, can change what one party is hearing compared to the other.
When we rehomed those noisy hens? OH MY, the relief! We're back to normal chicken noises for normal lengths of time.
Some questions to maybe consider...
1. How many breeds of chickens have you owned? Do you know if these are normal noises/volumes? The part where you said they all set each other off made me wonder, as quieter hens don't tend to do that.
2. Have you stood on her property facing your hens during egg songs to see if there might be acoustic differences in what you both experience?
As I said, I never would have thought it could be a problem if I hadn't been acoustically Tbtortured by chickens.