Women were the subject of portraits if they were famous like Queen Victoria, or famous, like Princess Mathilde, or both, like Empress Elisabeth. Mary Wollstonecraft Shelley was not especially beautiful, so she had to be famous. Not by a title, such as Marchioness or Duchess, but famous in some other way. If you feel like watching a Boris Karloff movie, here’s one reason why. Mary wrote Frankenstein (and other books). Or was it Trumpenstein? After watching Trumpenstein, get a jolt of juice from coal, breathe all of that refreshing carbon dioxide, warm up, and lurch off to war.
Her article in thepeerage is here. Her Wikipadia article is here.