The problem with a ball launcher is that she may sprint really fast after the ball and then suddenly stop to get the ball. I would be worried about the impact this sprint and sudden stop may have on my 1 1/2 girls joints.
My two are ball driven, so I give each one a medium size ball to hold in their mouths while I kick a larger ball around. They are extremely happy with this type of ball play - it satisfies their herding and prey drives and they don't sprint, they do what a GSD is suppose to do - trot. Much better for their hips and elbows, not to mention it really helps with developing their gait.