This is a good question, because the story doesn't really go into detail about her thoughts, feelings or fears.  Instead, it only shows what she does.  So, we have to infer what she is feeling, based on what she does.  If we look at the passage, she doesn't show much anxiety or stress over discovering that she has stepped on a corpse.  When her foot becomes caught, it states that she

"reached down quickly, unafraid, to free herself. It was only when she saw his naked grin that she gave a little yelp of surprise."

So, she was not afraid, and the only emotion she exhibited was surprise.  Instead of horror or fear, she was startled, and then, it describes her looking about the spot "with interest," not fear.  She was curious.  It was just a body, an inanimate object.  In fact, she even moves the leaves a bit to get a closer look.  She is calm and unaffected--she even stoops to pick another flower for her bundle.

It is only when she discovers that he had been hanged that Walker indicates any emotion beyond curiosity.  At this point, Walker uses symbolism and suggestion to imply a deeper meaning. When Myop realizes that the man had been hanged, she "laid down her flowers," symbolizing the end of her happiness, innocence and childhood.  Another symbolic statement to indicate how profoundly Myop was affected is "And the summer was over."  These two statements, even though they don't say, "Myop was really disturbed, and felt like everything had changed for her; she realized that cruelty and evil existed in the world, and so couldn't go on skipping around collecting flowers like a child anymore," symbolize that sentiment.  It's a more effective way to communicate that Myop was affected by the realization that she lived an a world where people killed each other; her innocence was gone, and she faced the cruel world of adulthood.

I hope that those thoughts helped; good luck!