Why did lily feel obligated to protect Connor?

Lily is Conor's schoolyard friend, and her mother is a friend of Conor's mother. Lily is a steadfast friend to Conor who watches his struggle from afar, even has Conor keeps her at arm's length. Because she knew of his mother's cancer first, and showed him sympathy when he did not want it, he directs his anger towards Lily. She takes this treatment well and never abandons the friendship. In the end, she provides a much-needed release for the boy when she tells him, "I see you."