If she's getting knocked over easily, shut her away from the others. It'll give her a break, and her kids will keep her company anyway. Her face being fluffy could be her being cold, it can make her hair go fluffy on her face which makes it look swollen. The itchiness leads me to think it might be an idea to give her something for lice/fleas. We use spot on, but you can't use the milk for human comsumption afterwards. However the itchiness probably isn't the base cause of what's wrong.
What are your minerals like? Is your area known for Copper deficiency? Copper deficiency can lead to anemia, and my mother (the vet) says it can also cause the scouring.
Make sure she does not have coccidiosis..........get dung tested! You said you got her last year, what can happen is that goats build up a resistance to coccidiosis, however they build up a resistance to their local strain of it. When moved and you will have coccidiois on your land, she could have picked up that strain and not had the same resistance to it. That can cause thin animals with the squits.