Three of the most popular women writers of all time are; J. K. Rowling (450 million books sold in the Harry Potter series + movie rights), Danielle Steel (800 million books sold (best seller of all time in Romance genre), and Stephanie Meyer (100 million for her Twilight series + movie rights). What makes them special? They are all different in their style of writing, yet they draw a huge audience.
I believe what sets them apart is the connection they all have with the readers who chose their books. People want to escape from the real world for a variety of reasons, so they delve into magical places or romantic lives of imaginary people. When a writer can bring the pages of a book to life, and readers can go beyond the paper its written on, then you have a winner.
These women have not only cornered the market with their great stories, they have overcome a market that was at one time predominately a man's world. The writing world is changing. The ebook market has hit the world by storm, but you still need to have a great story that people will want to read.
Watch the newcomers like Amanda Hocking (420,000 sold and counting) and Alice Sebold (118,583 sold) and see where they are headed. Alice is just behind John Grisham in sales with her book Lovely Bones. The writing world is changing faster than speed of light and women writers are ready for the challenge.