teeth and worming come to mind first.
Secondly how much hay are you giving her?
if you can get grass hay or if you feed her this anyway, you can always give her extra.
My friend has a hard keeper in the winter and we just give him 2-4 flakes of extra hay in the colder months.
Have you tried changing her grain? I’ve never heard of that brand of grain, so I don’t know how much “good stuff” it has in it.
"Take the time it takes, so that it takes less time."
"Expect a lot, accept a little, reward often."