She should have been slowly weaning them from 5-8 weeks of age. The little bit that is left there should simply dry up on it's own. It takes a few weeks for the mammary glands to return to normal again. If she wasn't slowly weaning them at those ages you need to be encouraging her to get out of the whelping pen and away from the pups for awhile.
Once you have got all puppies eating puppy moist foods you can dry up the mothers milk around weeks 5 to 7 but you must keep the mother away from the puppies for at least a week not totally cut mum off from pups as she will still want to play with the pups but the pups will also go straight to mums teats you just have to watch and be quick to stop the puppies getting mum otherwise it would be putting mum through drying up if a puppies did get hold of her its just the same in a dog as human,hope this helps