This was not entirely uncommon for the time, as female authors often used male pseudonyms to gain wider acceptance and readership. However, Mary Shelley was clear from the beginning that she was the author. In the preface to the novel, she even mentioned her age (19) at the time of its creation, further cementing her authorship.
While her husband's reputation likely helped the novel gain initial attention, Mary Shelley's authorship gradually became recognized over time. By the 1830s, she was openly acknowledged as the author and even began signing her name to later editions of the book.