I truely believe the dog is showing you she is thankful that you took her and her pups in. I took in a GS before from an abusive home (actually stole her in the middle of the night) and she was the best dog I ever owned. I personally saw the owner kick her and beat her and that is the only reason I took the actions I did. They know you are a caring person and want to do nothing more than please you and will do what ever it takes.