Complex sentence: Women who were newspaper writers at that time customarily used pen names, and for Cochrane the editor chose "Nellie Bly", adopted from the title character in the popular song "Nelly Bly" by Stephen Foster.
Split into simpler sentences: Women who were newspaper writers at that time customarily used pen names. The editor chose "Nellie Bly", adopted from the title character in the popular song "Nelly Bly" by Stephen Foster.