Complex sentence: It offered professional opportunities to women, as practitioners after just 12 lessons of study, who might otherwise have had none; 12 of the 14 practitioners listed in the first edition of "Christian Science Journal" were women.
Split into simpler sentences: It offered professional opportunities to women who might otherwise have had none. They could become practitioners after just 12 lessons; 12 of the 14 practitioners listed in the first edition of "Christian Science Journal" were women.