I just had my 31 year old guy put down a month ago today. He was eating a mix of Purina equine senior and Triple Crown Senior until the end. At first as a dry feed once/day for several years, then a mash once/day, then from this past spring until the end as a mash twice/day with a joint supplement and bute. The Purina did him well for a while, but then he started having trouble keeping the weight on. So, on the advice from someone here, I used TC and I'm convinced that's what kept him going, happy and healthy for as long as he did. At the end though, he would try hard to eat, but just couldn't swallow for some reason. We had to have him put down a few days later. He was always excited for food... he'd nicker as I came in to the barn and got his food ready... so when he quit eating the last couple of days I knew it was his time.
If you haven't yet, I'd give the TC a try. It certainly can't hurt. It was a wonder food for him. But if you can't find something she'll eat, and no reason why she wont eat, maybe it's just her letting you know it's her time. It's never, ever an easy thing, but it can most certainly be the kindest.
TM Tardy's Chick "Hunter" - 13 yo Paint
Remmy - 18 yo Morgan/QH cross
Gunner 3/31/11, Heidi 7/2009 Miniature Sicilian donkey