If this is a new problem (i.e. same goat produced god milk last year) and your other goat(s) now have nice tasting milk it will obviously be an individual problem. In the first instance I would probably give her a Cobalt vitamin type drench, a lot of people say that the foultasting milk is a Cobalt deficiency (?), but I think that is not the only reason. If you don't want her to milk buckets I would reduce her feed intake to take out all gaot mix, and only give some sugar beet shreds and maybe a handful of oats with it, and then go easy on milking her out every time. (It could just be that somehow the goatmix manufacturing got changed for example). Lots of grass, branches (willow is up here the only thing that is green enough) and hay (but not haylage).
I read somewhere in an old book that giving them lots of carrots produces "sweet milk", and mine absolutely love them (cut into long sticks, not grated). Unfortunately horse carrots are now finished and I am spending a fortune on Coop ones...
I am sorry I probably cannot help really, I haven't had this problem at all (but had mastitis), mine only get Caprivite once or twice a week, other than that I give (also once or twice a week) - a sprinkling of seaweed, flax/linseeds, garlic granules, comfrey leaves, ivy leaves and some other weeds that are out and about. (they absolutely love sticky willy, most thistles etc etc). I personally don't like the idea of giving supplemenmts on a daily basis, I have bought the new Adam Henson drench (prefer a drench to a powder actually as it gives more control over quantities), but haven't used it yet.... too busy lambing...