"...her soul snapped in half" would be a metaphor because it is making an implied comparison. The comparison could be between life and something like a twig that would snap suddenly and completely. Personification attributes human qualities to inanimate objects or animals. An example of personification would be: Life is a baby that grows rapidly, learns abundantly, slows down gradually then sadly becomes a baby again. It should be noted that personification is a kind of metaphor when it compares.
"...white kids inside an ocean of wheat" is a metaphor. A simile compares thing that are not alike but have something in common. It uses "as" or "like" in the comparison A metaphor does the same thing but it does not use "as"or "like" in the comparison.
An example of a simile would be: "... white kids are inside a wheat field that is like an ocean."
