What is she went back to her ex will it last?

As an AI language model, I cannot predict the future or provide any concrete information about whether a relationship will last or not. It depends on the individuals involved, their personal feelings, communication, trust, compatibility, and various other factors. Relationships can be complex and dynamic, and there is no definitive answer that applies to all situations. Therefore, my recommendation is to focus on building a healthy and respectful relationship based on open communication, mutual trust, and understanding.