Is it important to have the general light of women in the novel?
I'm not sure what you mean by this question. Is it a typo, and should "light" instead read "plight"? I'll answer it by addressing the importance of women's voices in the novel as a response to the dominant male culture. Remember, Mary Shelley's mother was the prominent author Mary Wollstonecraft Shelley. She's been identified as a "protofeminist" by many critics, meaning her writings, particularly "A Vindication of the Rights of Women" contain ideas/philosophies on the role of women in the world which would only become popular in later centuries. Although her mother died in childbirth, Mary Shelley was raised under the influence of these ideas, and this heritage speaks in Frankenstein as well.
Each of the female characters, including Elizabeth, Justine, and Safie are examples of what becomes of women in this masculine world. Safie is forced to leave her father and her previous life in order to join her love. If he had rejected her, she would have no recourse: alone, penniless, she would be at the mercy of anyone. Justine suffers execution at the hands of men for a crime didn't commit. Her word means nothing, and the only person who will speak on her behalf is also female. Conversely, the only one who can save her is male (Victor), and he instead chooses to save himself by keeping his secret. Thus she meets with the ultimate fate of a woman in a man's world: destruction.
Elizabeth suffers a very similar fate. Although she loves Victor, his feelings run close to obsession; certainly he feels as though he possesses or owns her. Their relationship is marked by secrecy and deception, and it is these secrets that lead to her death. Despite her kind, generous personality, despite the fact that she is more courageous than Victor (willingly standing up for Justine when he won't), she dies a violent death, ironically on her wedding night.