No idea why her feather won't come back.

[RI Chicken Man]

I thought it was molting but it's been months and has gotten slightly worse. Any clue on how to get her feathers back ?

 

[coach723]

That looks like rooster damage.
You can use hen saddles to protect the area.
http://www.hensaver.com/ sells them, amongst others, and you can make them yourself.
Just search for hen saddles or chicken saddles.
It can take a long time for the feathers to grow back.
Also, trim your roosters claws and spurs, and make sure your rooster/hen ratio is high enough.
She's probably a favorite and is getting topped a lot more than others.

 

[azygous]

It's hard to see from the photo, but are those prickly shafts broken feathers or new pin feathers?

Look closely. If you see uneven and broken feather shafts, your hen won't be able to grow new feathers until she molts. If those are pin feathers, you will see a pretty uniform array of tiny feather tufts sticking out of them. Those will produce brand new feathers over the next few weeks.

A closeup photo would help. Then I could tell you for sure if she's growing new feathers or not.