You don't even need to try to be the good person you already are. See, you already know how to have fun and be likable by just being yourself. It doesn't need to be part of some over the top schtick to impress people. When she does the rad girl thing it's like a disguise, probably covering up some part of herself she's unhappy with. But when you withdraw and cover yourself up like that, you're actually just preventing people from seeing someone who's already beautiful.
Terezi, find him. :cAlready on tumblr: [link]