Before becoming who she is today, she was a sweet and naive kid. She stood up for herself and others that she cared about. She would take the blame for others and protect the ones she cares about in the end. This caused people to use her for their needs, not caring about Jas in the end. 

After the accident, Jas is harsh towards newcomers and quiet reserved. She now watches everyone with careful eyes and doesn't trust anyone anymore. Jas prefers to keep to herself with her emotions and her problems. Though she does still care for people, but you mostly see that through her actions.