Why hadn’t he told her sooner?

Jason exchanged a meaningful gaze with Aiden, and it was not hard to tell his next move. He thought Aiden's confidence would waver, but it didn't. 

Aiden stood there with a smile. Jason's gaze warned him, but he didn't falter. Holding the smile that could win the world, he turned to Arwen and introduced, "Jason and I have been friends since high school, same as Jacob." 

Arwen glanced at Jason briefly before turning back at Aiden. She stared at him as if seeking some confirmation, her eyes shining with a glimmer of hope that slowly and slowly transformed into confidence. 

"Oh," she said, her lips curling up into a meaningful smile before turning to look at Jason again. "Dr. Clark is also my attending doctor. Because of him, I am able to walk today and have the chance to dance tomorrow. He treated my legs that was almost ruined in an accident. It's both a coincidence and a surprise. Isn't it, Dr. Clark?"