One thing that surprised me when I started gundog training, is how little retrieving is actually practised. And when you get more into it, it makes more sense.
If you pick the ball up for your girl every time, she doesn't need to bring it to you. Tau used to spit her retrieve occasionally, and I've been working on her delivery to hand, it has come on nicely now with only the occasional glitch. She gets retrieves on my terms, I don't just constantly throw the ball/dummy for her, so then it becomes not so much of a reward but 'the thing we do all the time on walks'. Tau knows that I've got the ball or dummy when we go out, and she is always checking back to see if I'm doing something that might involve a retrieve. Throughout a walk I'll recall her and praise her with a bit of a fuss for coming back, I'll also do bits of heelwork, and stops with her sitting to heel; all of these are just basics that she can easily get right and be praised for, and I use that to build on for her other training. You might find your recall improves if you have that reward factor involved with a possible retrieve as well.