In 5th live concert there are intermission dramas. In one of them, Maki defeated Rin in mochi eating competition by tricking her (to sprain her own neck, poor Rin), saying "No one said it's against the rules, right?". Also in a drama CD track (I forgot which one it's from, the one where the first year ran a maid cafe), she also tricked Honoka a bit, no harm done, though, just super hilarious.
And when listening to her solo and songs she's the center, my mind started giving her more dark, mature image.
But I totally agree with you about Maki being hardworking and naive in the anime. That's what I love about her, a know-it-all who believes in Santa Claus? Made me fall for this character right away.