Yes, let her go. No need to engage in extra battles with her. Your sitch sounds a lot like Thinker's. So you might want to read the history of his threads.
You won't win by being nice to her. Ask yourself why she is still there. She claims to be so unhappy. Why doesn't she leave? She is staying for reasons that make the marriage desirable to her, maybe economic support. You will only get a reaction from her when you show her that her behavior is jeopardizing her life choice. Let her know that if she is free to leave. If she chooses to stay, then she needs to act appropriately. Demand things of her. Don't let her be a spoiled teenager sulking in her room, distaining the people around her who make her life of luxury possible.
