At two years old, has she ever had a real molt? Usually around a year from when they begin to lay, they have their first molt.
I had a Brahma of the age of your girl who was in what seemed to be a permanent molt. I posted here asking about it, and someone suggested that she may be in, what they call, "stuck in molt".
To jolt her out of it, you need to feed her a massive amount of high-grade protein. Scrambled eggs, canned tuna or salmon, yogurt, etc. It worked for my girl, and she responded by growing in beautiful new feathers.
But on the other hand, I had a two year old SLW rooster who looked like he was going through molt - very scraggly, two tail feathers, and he died suddenly one night of an apparent heart attack.
If I were you, I'd assume she is stuck in molt, if this condition began when she molted. Feed her as much protein as she'll eat at one feeding each day. If it's prolonged molt, she'll show signs of improvement in a few weeks.