The Nature of Jade by Deb Caletti.
Jade DeLuna suffers from panic attacks, but she doesn't want her issue to define her. So, she takes on a job working with the elephants at the zoo. Despite their enormous size, they serve as a calming influence in her life. That is how she ends up meeting the boy in the red jacket, a boy who brings his infant son to see the elephants. The boy looks too young to have a son and Jade is intrigued and desperate to meet him. As she secretly weaves her life into his (afraid others will warn her off of him because of his adult responsibilities), she discovers the truth of his own story and must confront a painful decision of whether to follow love on a complicated path or seek safety.
I'm not sure it is an adequate comparison title, so I will continue seeking similar ones, but it was a good read. The characters were believable and conflicted. The plot moved at an adequate pace. Moreover, I enjoyed the snippets about animal behavior that prefaced each chapter. While the novel was definitely different from my own, it shared some similarities in highlighting anxiety. For teens seeking a novel about individuals with panic disorder or teens interested in learning about elephant behavior, this would be a good fit.