“She did not remove her gaze from the darkening countryside, but for some moments was quite silent; then turning to him with a sudden passion in her manner, that lighted up her face with a new and wonderful beauty which the baronet perceived even in the growing twilight, she fell on her knees at his feet.” (Bradon 17)
Though the passage initially just struck me simply as an oxymoron (how can darkness cause so much light?), this passage can be used to further ensure that Lady Audley was previously Helen before she took on her new life. The contrast of light and dark symbolizes her quickly changing thoughts of getting married to Michael. When she looks back on the growing darkness, she is having negative thoughts on getting married. Firstly, if she is Helen and marries Michael, she will be going against the laws of marriage with George. Furthermore, marriage will force her to give up hope that George, the one Lady Audley/Helen truly loves, is somehow alive and will return to her. Afterwords, she realizes the upsides to marriage, and the darkness lights up her face. She will never have to be worried about her past again. She can live openly as wealthy, cheery Lady Audley and leave Helen behind. Her past may seem dark in some ways, but she can take advantage of the darkness and hide in it.
However, even the baronet can see the growing twilight, as mentioned in the penultimate clause of the passage. This may resemble an example of foreshadowing; if Lady Audley shines too brightly, she will have no darkness to shroud her. She may be free of Helen for now but Lady Audley should still proceed with caution.