Fetch can be broken up into a number of different tasks, and then combined into a final routine.
The first part is the chase. Sounds like your girl has that down pat.
The second part is the pick up...which your girl has also already mastered.
The third part is the retrieve, which is basically just a recall.
The fourth part is the release.
You can practice all the parts separately. Since your dog already has the first and second part down, start working on the recall and release.
The way I work on recall is to train them to come to the whistle, although any command (verbal, hand, whistle, etc) will work. Then, as we're wandering around the house or yard, I'll give the recall command and reward with whatever turns them on--pats and praise with the occasional treat keeps ours coming.
At the same time, I'll train for the 'give'. Offer a toy with the command 'take'. When she takes it, praise. When she gets the idea of 'take', I'll spice it up. When she takes it I won't release it. So she's got one end, I've got the other. Tell her 'give' and when she releases it, praise her up, and give the toy back to her. (If you have trouble getting her to release, try blowing softly across her ear opening.
Seriously, it works!
) You give the toy back so that she realizes she's not going to automatically lose the thing she wants by being an obedient girl--makes her more likely to want to cooperate.
Once she has the idea of 'give' and her recall is good, put everything together.
Toss the toy, wait till she picks up; give your recall command; when she approaches, use your give command. It might take a few weeks, but this method has worked for us. And when the dogs figure it out, you can see that they're quite pleased with themselves.
