Diggedy, if you are trying to find a food already in the directory which has the nutritional characteristics of a diet for liver disease, then - using the table for guidance - the search would be for low protein (of high quality), high fibre, low copper and low sodium.
And yes indeed this is not as easy as it may appear, compounded by oft unclear labelling of pet foods regarding amounts of copper for example.
Helpfully, there are useful filters available in the allaboutdogfood Dog Food Directory to narrow down food choices and hopefully may provide a canned/dry food to help her.
The characteristic of low protein (of high quality) may be found using the "Food properties" filter set to "Organic" or "Natural" (or both of these). Plus using the "Nutrient levels" filter, it is when the slider for the "Protein levels" is moved accordingly, the corresponding results would be of foods with lower protein levels.
To find the characteristic of high fibre, then using the "Nutrient levels" filter, moving the slider for "Fibre" accordingly results in foods of high fibre.
It is not an easy task to filter out, completely, all foods with salt (sodium); yet any foods that have "added salt" can be omitted by setting the "Avoid ingredients" filter to avoid "All red ingredients". Thus the foods that are avoided will include those with artificial additives, and also those with added salt, as both add extra strain on the liver.
Unfortunately, there is no current filtering of foods with copper. However, the aim is to reduce copper stores in the body and so prevent an accumulation of copper in the liver. Absorption of copper is enhanced by high dietary protein and is reduced by zinc, fibre, and ascorbate (vitamin C). The Samylin is providing vitamin C, fibre is being increased following the table guidance. So this leaves zinc and it may be prudent to research into whether adding a zinc supplement might be appropriate.