This quote from Eudora Welty's "A Worn Path" is probably simpler than what you think. Phoenix isn't being metaphorical. She simply means that the ground here is easy to walk on, compared to what she has already been through. She also tells herself to "walk pretty," because the walking is easy here. She is "getting herself together" after the difficult walk she has already been through. She has walked up a difficult hill, walked through a section of woods where there is no path, etc., and is now relieved to be on an easy stretch of the journey to town.