Answer:
The phrase "wild, horse of a woman" used to describe Esperanza's great-grandmother is an example of a metaphor. A metaphor is a figure of speech that compares two things by saying that one thing is the other, without using the words "like" or "as." In this case, the metaphor compares Esperanza's great-grandmother to a wild horse, suggesting that she is strong, powerful, and perhaps even a little bit untamed or unpredictable. This metaphor helps to paint a vivid and memorable picture of the character in the reader's mind, and adds depth and color to the description of her personality and qualities.