I had a similar but slightly different thought. I'd explain to DD that the boy may have a great deal of insecurities, impostor feelings and other anxieties and he doesn't seem to know how to properly deal with these feelings. I'd explain that many talented people are highly self critical and over reactive to the criticism of others.
It sounds like he has unhealthy perfectionism that's negatively impacting his relationships with others. I'd ask DD is she's ever felt that way and brainstorm ideas that could decrease the boy's insecurity rather than increase it. It may help empower DD if she can understand the long term negative consequences of the boy's action and the unhappiness he must be feeling. Good luck!
