There is a GREAT book that I am reading right now, that I actually got for my other two dogs, who are labs. I seen the author on Oprah, and she has an AWESOME book called The Loved Dog. They talk about this over protectiveness in the book, you should get it and read it!! The author is Tamar Geller, and its a great way to teach and undersstand your dogs!

Good luck with Sadie!!!

Amber