Juxtaposition in Character Development

Read the following excerpt from a fictional narrative:

As rain drummed against the window, Claire stared blankly at the page, the plot of her unwritten novel swirling in her mind like the storm outside. Her thoughts flickered back to the moment she lost everything—her family, her home, her dreams. Each tear that fell outside felt like a reminder of the walls she had built around her heart, keeping out both pain and possibility. But today was different. Inspired by a memory of laughter, she picked up her pen, each word slowly chipping away at the fortress she had created.

Based on this excerpt, which structural element most significantly contributes to the development of Claire’s character?