Watching Derrick flee, Janine didn't give chase. Sometimes, a good therapist had to let a patient get angry. Anger was better than complacency, unless the anger turned destructive.
In Derrick's case, she didn't think he would harm himself or others. Not intentionally at least. His decision to avoid his family might seem selfish, on the surface at least, but she was trained to look past the words to the cause. Derrick is afraid of hurting his family. Not physically, but emotionally. Within close-knit families, if one person hurt, they all hurt.
Derrick understood his family would grieve his loss of mobility with him. Understood they'd do anything to make him feel as if nothing had changed. Would give up their lives to help him.
He didn't want them to do that.