No, she wasn't a traitor to the Resistance, but she was a traitor to her ideals. Any last remnant of hope for a better world was crushed in the days immediately following the Final Battle. Lord Voldemort's surviving Death Eaters made certain of that. As she was confined to a small broom cupboard in the castle that had miraculously avoided any kind of damage, she'd been given the opportunity to think about what she was going to do next.