RE: Retrieving in thick cover crops.
Sounds to me that things are working for you as they should. Although an experinced dog will use sight, sound and smell for locating falls, a novice dog needs the help from the hunter to mark the falls. My advice is to continue as you are and the dog will eventually take over as she gains experience. You should continue to mark your falls though, as even the best of dogs need a hand every now and then.