Nursing that many puppies takes a ton of energy, she needs to be fed quite a bit more than what she would normally get. I don't know about Blue Buffalo, but the puppy food that we had listed how much a nursing female should be fed, try sectioning her meals out into smaller amounts and feed more often (like two cups every 3/4 hours) so that she doesn't over eat and get sick. She should also have access to water 24/7. Cottage cheese probably isn't the best thing to give her just because some dogs cannot digest the lactose in dairy products, try goats cheese/milk as a replacement.
If she's too thin she needs to be seen by a vet, they can provide medication to give her. My vet gave us a calcium supplement to give her, and recommended a food higher in fat content.