There is New story from JK Rowling about Professsor McGonagall, and it's three parts in book1 where JK Rowling has added McGonagall story. And how to unlock McGonagall in pottermore?
Just Go to the screen where you're supposed to unlock her (Chapter 7 ). Zoom in once. She's standing to the right of the door to the great hall. It's dark, but she's there. Just click her. Her back story is possibly the most interesting unlockable info available so far!
About new Story of Prof Minerva McGonagall in Pottermore (New from JK Rowling) you may find it in the sidebar archieves :
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