Your puppy is entering "toddler-hood" and it's totally normal. Expect some loss of brain function as well.
Just remember that a tired puppy is a good puppy, keep her active and entertained and she will be better. You might even consider entering her into a puppy class or an obedience class to keep her brain engaged and active. As several people have posted it only lasts for awhile and then the brain comes back and they settle down. Enjoy it while it lasts.
Teresa