First welcome to PT! Kudos to you for helping such a dog in need, and puppies too!

It's hard to say if it she starting to show aggression or just protecting the puppies.
No breed of dog actually "turns" on their owner, it all just boils down to individual genes & how they are raised. Even the dogs that supposably "turn" probably have an underlying reason as why they acted the way they did, it's just that the owner wasn't able to read the dog correctly or ignored previous warnings.

Either way since your dog is still young & her puppies are going to their new homes it seems like this should be fairly easy to resolve. Getting her enrolled into a reputable obedience class (this will help with socialization, training & bonding) should help tremendously. And also practice the NILIF. Here is a good site w/ more info. http://www.goletavet.com/nothingfree.html

No matter what your decision may be it is wise to practice the above suggestions. So if you plan on adopting her out please strongly reccomend the new owner does the same. You can even make up a contract stating that obedience classes are a must & part of the adoption deal.