This morning we took her back to the vet (who was back from leave). The good news is that she weighed in at 28 kg. Deduct the weight of her jacket (it was very cold) and keep in mind that initially when we found her, she was dehydrated, then I think we can look at a total weight gain of about 5 kg of flesh added to her bones, despite her intestinal problem :-).
Dr. de Villiers confirmed that the mange was not yet under control, and prescribed more medication for that, and another course of antibiotics (targeting the pathogenic intestinal bug/s), as well as a short course of cortisone, to give her relief of the obviously irritating itching. She also suggested we change her feed to another type, at least until her intestines have settled.
We do feel a bit more positive now, and trust that from now on, there'll be progress only, and no more regression.