The significance of the conversation between Sierra and her friends about how their neighborhood is changing is the foreshadowing of the shapeshifters.
<h3>What is Foreshadowing?</h3>
This refers to the literary technique that is used to show the prediction or hint about future events in a story.
Hence, we can see that although your question is incomplete, I can infer that you refer to the book <em>Shapeshifter</em> and the foreshadowing used shows the mayhem that is about to befall the neighborhood when dark shapes begin to move as they are possessed by spirits.