Okay, I was thinking she could be. Is she bloated a lot? Compare her to another hen.
She likely has a reproductive issue, and if she hasn't been laying that's another sign of it. The tail pointing downward is also a sign.
It may be hard to know exactly what reproductive issue she could have. It could be Salpingitis (if she has that she will be expelling lash eggs, which is basically pus), Egg Yolk Peritonitis, Internal Laying, ect...
Bloating of the abdomen can also be a sign of ascites, which is from organ failure. The organ will leak fluid and it accumulates in the abdomen. I think its reproductive though due to the tail pointing down.
Unfortunately in most cases there's not much you can do. But you could give her some antibiotics and see if it helps. I believe the suggested one for reproductive issues is Enrofloxacin.