Teach her the "leave it" command. Practice with things lying out in your yard which entice her and keep walking when she shows an interest to get at them, saying, "leave it." You can use this for so many things. I wouldn't make too big of an issue over the leash playing though. She's a pup and as it was said, she'll get over it. It shows she likes her leash and that's a good thing. Just reward her when she "leaves it" and get her interested in something else. My 2 yr. old Dobe plays with his leash sometimes and I actually encourage it because he's so cute, shaking and flopping his paws all over the place. Then I tell him, "enough....leave it." And he gets back onto the business at hand. LOL. Let your pup be a pup...don't take things too seriously and meanwhile, teaching other things will start to fill up his brain and he'll leave childish things behind. LOL.