I think you should not be taking her out away from the pups yet, for one thing she may pick someone thing up on the pavement or from other dogs, and bring it home to the pups who are vunerable imnunity wise at the moment, and also because it can stress her out too much, if she was hightly stressed while on the walk, because she had been made to leave her pups unattended, this may have triggered the unusual intensity of her attack on the pup, which she may have normally just give a good telling off to for the same offense(what ever it did), the other problem is she may get too used to being away from the pups and stop feeding them, it is still too early IMO for them to stop feeding from her at the moment. edited to add the digging may be a sign of stress after leaving her pups for so long, and until her mind is completely settled this isnt going to happen again she may show some signs, like the digging, also my bitch bled for a couple of weeks after having the pups naturally, I took her to the vet who advised me if it hadnt stopped in a week he would give AB's the bleeding did actually stop a few days after this. her 2nd litter was born by C Section, she only had a little discharge afterwards, which I presumed was the after effects of being cut, this cleared up after a week or so and was not heavy, if she continues to have discharge it may be worth mentioning it to the vet and AB's may be require, this could also be adding to the digging.

Mo