Mari due to being left by her dad at a young age, she is at first cautious with who she allows herself to get close to.

She is constantly afraid of people leaving, and she sometimes replays scenarios of it happening even though she knows it'll never happen.

But, although she knows that it's not real, sometimes she'll wake up at night afraid she was left by everyone.

She is very much the "I don't care who started it, i'll finish it!" kind of person. Especially when Jean and Eren fight. With that she'll get right in the middle and slap them both upside the head.

Especially when she's in a mood where she's not willing to put up with your bull crap.

And because she's afraid of people leaving, she will often checkup on people she cares about, so she can determine whether or not she should be worried about them leaving.