Is she sick?

We have a hen who is becoming a recluse and acting strange. For the past few months, she's had a "dirty" bottom but otherwise fine. Today I went out and she was in the nesting box and a milky white slime was ozzing from her rear. Shes a bit lethargic too. Her comb also looks about half the size it was a few days ago.
I nudged her a bit to leave the box and she did. Jumped up on to the roost. When she pooped, it was a huge amount. It was a little white pasty substance with a huge amount of a BRIGHT green slime. Smelled bad. She hopped down walked out and got a drink of water and went back into the nesting box. She's just standing there with her eyes closed.
Her wings are also a little extended downward instead of tighter to her body.

I looked up the poo and it seems closest to what they are calling Broody Poop.
We've never had a broody hen before and dont know if any of this is normal.. Is very odd. Can anyone help?!!!
Thanks.