Anna comes from the world of spreadsheets and risk assessment. She likes logic, predictability, and knowing where her next meal is coming from. Being dumped barefoot in a fantasy world with a game-like HUD and zero explanation was not her ideal Tuesday.
Where Mimi charges headfirst into danger, Anna hangs back and calculates. Where Mimi sees a fight, Anna sees opportunity cost. They shouldn't work as a team. They do anyway, mostly because Mimi doesn't give her a choice.
She wants to go home. Not be a hero. That's the deal she's quietly making with herself every day she survives. Find the way back, keep her cat alive, don't do anything brave. It's going well so far, except for the small problem that the world keeps handing her situations where doing nothing isn't actually an option.
Anna's the reader's anchor. If Mimi is the heart of the story, Anna is the voice in your head going "wait, we're really doing this?" right before they do it anyway.