Sticks are good. I can't imagine what you would have done if she was getting out of the water with a duck in her mouth :)

I don't have personal experience with Golden Retrievers but I have raised a few dogs and 6 years sounds too soon to be called old. Maybe it is something temporary that annoys her and keeps her from going full speed. But even if she isn't the fastest any more it doesn't really matter, does it?

She is still adorable :)