Petra was a relatively short woman. In the manga, she was portrayed with blonde hair and blue eyes. However, in the anime, she had light ginger hair and amber-coloured eyes. She wore the typical uniform of a member of the Survey Corps
Petra looked up to Levi as a captain and cared deeply for her team, though was notably at odds with Oluo.
Petra was kind and caring, as shown when she looked after and guided Eren when he was first admitted to the squad. She seemed to have acted as some sort of attachment figure for Eren among Levi's Squad as she was the one shown to worry about him. Although all of Levi's squad wished (and demanded, to an extent) Eren's unconditional trust, it was ultimately Petra who convinced him to do so.
Despite her kind nature, Petra was a conditioned soldier with a quick reaction time against perceived danger, such as the time when Eren accidentally transformed into a half Titan, she took an extreme reaction and interrogated him alongside her squad. She also displays extreme loyalty to her leaders and superiors and their orders.
She also showed the most remorse over her reaction to Eren's accidental transformation. Along with her comrades, she had bit her hand just like Eren, signifying that they had established a close bond.