Thing is, Georgiou hasn't changed one bit. Although it's played for laughs, she suggests mass destruction, genocide and as the OP pointed out, laughed with glee when her enemy died in agony. She's expressed zero regret for past actions. The only reason she's an ally is her love of Michael.
Completely changing overnight would be unrealistic, don't you think? Have we seen Klingons change overnight? Yeah, Seven did practically, but how realistic was that? And how quickly did Seven come around to feeling remorse for what she did, or the cannibalism she commited after she was cut off from the Borg collective?