I don't have any immediate recs off the top of my head (I mean, aside from the constant "Chosen and Defined" rec, but that's listed in the link from someone else), but for all your femslashy goodness, someone hosted this one recently:
Chosen and Defined: https://archiveofourown.org/series/5654 St. Trinian's, tons of expansion on the fandom as a whole, lots of characters, some amazing twists and excellent moments. Basically: if you want fic about women kicking ass, getting knocked down, getting back up, joking, laughing, loving, etc., this is for you.
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https://sylvaine.dreamwidth.org/155122.html
Chosen and Defined: https://archiveofourown.org/series/5654
St. Trinian's, tons of expansion on the fandom as a whole, lots of characters, some amazing twists and excellent moments. Basically: if you want fic about women kicking ass, getting knocked down, getting back up, joking, laughing, loving, etc., this is for you.
There are also spies involved.