Oh your poor pup. 
I don't have experience of Giardia, but my - now big strong galumphing two year old Lurcher - had Campylobacter when he came to us as a pup.
Like your girl, he had the most dreadful diarrhoea from the day we brought him home. He was an emaciated, very poorly pup, but the rescue insisted he'd been fine there, so refused to inform the people that had rehomed the other puppies he was housed with. 
I would be very concerned/suspicious that she came to you with the problem/s, particularly as, according to my vet, these sorts of infections are often due to poor husbandry on the part of the breeder and very common in 'farmed puppies'. My boy was a rescue, dumped in a ditch at birth, so the likelihood in his case is that he picked up the infection from being in unsanitary conditions before he was found at less that 24 hours old.
As I understand it, Campylobacter is pretty common in the digestive tracts of dogs and not usually an issue for healthy adults, but can overwhelm the healthy gut flora of pups as a result of other illness or stress, including the stress of going to a new home. I don't think the same can be said of Giardia or EColi though, but don't quote me on that.
We were advised to keep him on just plain chicken (nothing added, so no rice or anything) for several weeks and at first he was on 8 meals a day, so it was both costly and time consuming. He recovered and gained weight well on that and we switched him to a good quality kibble once we were given the all clear by the vet.
My pup eventually tested clear, after three rounds of antibiotics (repeated courses are often necessary) and had his vaccinations at about 17 weeks, but he gained weight and condition and was doing healthy looking poos quite a while before that. (We had to carry him everywhere for socialisation and having grown to 28 1/2 inches to the shoulder, you can imagine how big and heavy - not to mention how long his legs were by then!)
Hygiene at home is really important, especially if you have young children. I seemed to spend all day either cleaning, cooking chicken or feeding him for the first few weeks. We also restricted him to one area for toileting and bleached that area every time he went and made sure his feeding and water bowls were sterilised after each feed as well.
He has never had a reoccurrence and had had a healthy digestive system ever since.
I have also had two adult dogs that had severe EColi at the same time. It took several rounds of strong antibiotics to clear it and they both had dreadful diarrhoea at the same time. Big dogs too, so we were awash. 