In defense of Cody Horn
I watched the movie twice, and the first time all I picked up was the blatant and obvious lack of chemistry between her Tatum, and how she always looked miserable.
I've never seen her in anything, so can only go based on this. Perhaps her character is so miserable across the board because she's being treated poorly right out of the gate, she's taken advantage of, she tries to help and offer help but is just met with disapproval/disdain in many ways.
Her boyfriend is a total ass who is very controlling and in fact, has less personality and duller than Horn could ever be. He's just a douche in all senses of the word.
Her brother is living off of her and not contributing, he's not going to job interviews, he's losing jobs, he's not even willing to TRY. Once can imagine how long she's put up with providing free digs for her mooch of a brother.
When her brother finally does get a job, (put aside in her opinion she may consider this behavior lude, in part because of HIS behavior on and off the stage, unlike Mike who has more to his life)...and he gets strung out on drugs. The months that pass across the screen may only be a part of it, but that's a long time for Horn to be treated like a doormat. I would be surprised if she was running around feeling perky and joyful and exhuberance.
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Sic vis pacem para bellum.