After Jane finds out about Bertha, she locks herself in her room and grieves over what has happened. Then she starts to think about the second thoughts she was having about marrying Rochester and the dreams she had. This makes her realize she must leave Thornfield. Rochester then offers to set her up as his mistress, and Jane refuses. She is torn because she doesn't want to add to Rochester's misery and knows it will be hard to find someone else who loves her as much as Rochester. But she also knows that living with him would compromise everything that Jane believes in. By marrying him, she would always feel indebted to him because he is of a higher social class. More importantly, Jane would lose her self-respect and would be giving up control of her life to Rochester. She knows marrying him is morally wrong, and she cannot give in to rejecting her values in a time of weakness and emotional stress. She must leave or she would feel like a prisoner, both spiritually and intellectually.
Jane does struggle with leaving Rochester, but she knows it's the right thing to do. Of course, she feels hurt because Rochester offered her the love she had always wanted. Any woman, even today, would feel hurt and betrayed if she discovered her fiancee was already married and had lied to her.