Hen has hard area between her legs

[NatJ]

The mass or tumor is getting harder, almost like a rock.

Just to check the obvious-- have you felt any of your healthy chickens, to make sure they do not have that too?

(You wouldn't want to focus on the wrong thing, when trying to figure out what is wrong with her.)

I don't feel that she will be able to recover.

I'm going to put her down, of course I don't want to but I will not let her suffer.

Sad, but I think that is a reasonable decision.

 

[Wyorp Rock]

The mass or tumor is getting harder, almost like a rock.

I don't feel that she will be able to recover.

I'm going to put her down, of course I don't want to but I will not let her suffer.

She is not a year old yet.

I'm sorry to hear that.

If you do put her down, then consider sending the body for necropsy at your state lab or if you are up to it, then perform your own informal one. You may be able to see what the hard mass is.
https://www.metzerfarms.com/poultry-labs.html