She didn't self exile as punishment for her actions. Hell, the last thing said to her was that the people of Westview, that she kidnapped, abused, and tortured, would never know what SHE gave up for THEM. She went to be alone to process her grief in a healthier way and learn who and what she truly is from the book. She ends being emotionally healthy with even more powers than before and Rambeaux, Darcy, and the FBI treating her as a hero for her actions. That's not a "punishment". It's a reward.