Wow, I'm pratically speachless... Poor lass... and it only took a year... wow...
*blinks and tries to recall feed knowledge* I think bran mashes are good for helping put condition on horses, especially if they have lost appitite. Linseed jellys are good, although a lot of preparation if you can't find a pre prepaired supply. Barley based feeds and feeds with peas/beans and soyabean meals are also used for weight/condition gain.
Try to avoid overly starchy/sugary feeds as these often lead to digestive problems, especially if she's not used to them. Fibre is ALWAYS good, so I would also give sugar beet and a chaff -alfalfa if the vets says its ok. Alfalfa is great, but it isn't suitable for some horses.
You can get complete 'conditioning' feeds too. They're mainly based on what I mentioned above. Some veteran feeds could be suitable too. If you buy them in pellet form, you can soak them into a liquid meal if her teeth aren't so good either.
So glad you found her again and are going to offer her the care she deserves!
We lose ourselves in the things we love, we find ourselves there too ~Kristen Martz