I think Clara's personality being somewhat different week by week is actually part of the story arc. One of the reasons she's the Impossible Girl. She has become one of my favorite Companians of all time.
It is interesting how Clara is (or the Claras
are) able to easily slip into any role a situation demands. She took command of that (albeit second-rate) military unit with little hesitation or fear, almost as if she was a trained officer.
It's quite complicated...