I have questions!

If I throw a ball/bumper/frisbee for Gabs in the yard or at the park, she'll run out after it, pounce on it, and then go out to do whatever else she wants. However, if I throw it in any sort of terrain- high brush, wooded area, the lake- she will go get it and bring it back. Why is this? Is this because the regular land retrieve is boring to her? If so, how do I make more exciting?

Also, I would like to teach a formal "take it" and "fetch." Right now we're just throwing the ball (no commands). All the literature, etc, that I can find seems to involve force fetching, which is not something I am comfortable with. Can someone recommend another method of teaching this?