The Fault in Our Stars: Why would Hazel be concerned about spoilers?

Because she didn't want someone to tell her she wanted to find out on her own

Explanation:

at the beginning of the story, elisa just has the small idea of wanting more attention, but as the story progressed, her desire for more attention grew larger. before she talked to the man with the wagon she was just focused on her chrysanthemums but when she talked to him and got some attention she enjoyed it, so she decided to get all dolled up for henry. but when they were on the way to dinner she was so upset because she saw the flowers on the side of the road and realized the man didn't take interest in her like she thought.