I can certainly appreciate the area you are in and the ease of walking out leash-less, however, your very young pup is vulnerable to a number of dangers by not being leashed. Aside from gopher holes; coyotes can easily take advantage of this setting, and in a pack situation you would be helpless to defend your pup.
Aside from the safety issues, she is not learning respect for you or the leash by walking without it. You can walk out with her on a 6' leash and practice her walking by you; and then on the return trip put her on a long line for some 'restricted' freedom, or vice-versa.
I live in an area surrounded by fields and woodlands and have exposed my girl to these areas since she was a young pup. She was well over the age of 3 yrs and after we had completed 3 yrs of Obedience schooling, before I attempted off-leashing her.
There is time for off-leash when you have a respectful and well-trained adult dog. By allowing her this much freedom, you are setting a precedent for the future which will be difficult to undo.
Is she currently in a training class?
Best wishes-
kathy