She probably isn't a German Shepherd Rottweiler X if she is full grown and only weighs 50 pounds. It seems like a mixed breed dog of those two breeds would be fairly big, male or female. I have a German Shepherd Border Collie X, and you're dog resembles it a little bit, so maybe you're dog is a Rottweiler Border Collie X. Let me ask you this, does your dog ever tilt its head and stare at you like it's wondering what you are thinking (a common Border Collie trait...I think) or also, does it have hearding instincts such as running full speed at birds then going immediately going into the down position then start running full speed at other birds as if herding them. And if you're dog is fast, like extremely fast w/ incredible endurance, then it might have Border Collie in it.

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