I had to resort to putting a peeper on my JG to keep her from pecking at my BO. And I feel awful about it. But she's not fighting it. AND she's not pecking. If I can just do this for a few weeks. Maybe a month. And build up the BO's confidence and strength because now she can eat w/ out being pecked, then we'll be good and I'll take it off.
In my opinion you should worm each and every chicken individually, orally, with the Valbazen, asap. Worms can cause a variety of symptoms including weight loss and death. If your chickens are more than six months old and have never been wormed, the way she is acting, and with the weight loss, I would worm her.. if she isn't having any laying issues.. but then, worms ( as well as the shorter days and colder weather ) can cause them to stop laying, too. Molting can cause them to be more grumpy and all....
Do you know how to give oral medications? And, do you know how to worm with Valbazen? (if not: search here on BYC for "worming with Valbazen" and "Valbazen dosages" and "giving oral medications"... "eggbound", "molting", "weight loss", etc... you can get a lot of good info from dawg53 on worming. And, lots of info on all the other topics by using the search here as well.
Pumpkin seeds raw and ground up, and mixed with buttermilk are good fiber and probiotics.. but, will not worm her. You can give that three days after each (x2) treatments of worming with Valbazen.. withhold eggs until 15th day after second worming. to 25th day total. (Tapeworms take more treatments than the normal two)