[QuickSilver]

There is a really cool concept in training, which is that you teach a complicated trick backwards. This applies to fetch in that you teach your dog to Drop It first, right near you.

I also rewarded Thor every time he brought the ball back somewhat near me, then to me, and then when he was actually dropping the ball in my hand. He got really good.

Then I tried to phase out the treats, and he decided keep away is more fun. He'll only bring the ball back if I give him a good treat. He's a total mercenary!

Also, as others mentioned, wait maybe a minute if she doesn't bring the ball back to you. This will help her make the connection that if she wants the fun to keep going, she needs to give you the ball. As a reward, if she brings it to you, throw it for her right away.