Petra Ral

Species
Human
Gender
Female
Height
158 cm
Weight
55 kg
Relatives
Ral family
Unnamed father
Birthday
December 6th
Residence
Wall Rose
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. She displayed extreme loyalty to her leaders, superiors and was ready to react in any given moment, such as the time when Eren accidentally transformed into a half Titan.
She also showed the most remorse over her reaction to Eren's accidental transformation. Along with her comrades, she had bitten her hand just like Eren, signifying that they had established a close bond.
During an expedition outside of Wall Rose, Petra is left to tend to injured soldiers while Levi kills nearby Titans. One of the soldiers, despite Petra's efforts, bleeds out from his injuries.
The Female Titan arc
After the post-Trost District battle trial to decide Eren's fate concludes with Eren joining the Survey Corps, the Special Operations Squad is assigned to look after him. Petra, along with the rest of the squad, accompanies Eren to the former HQ of Survey Corps, which will now serve as a hideout for Eren. As the hideout has not been maintained well, Levi orders everyone to begin cleaning. During the cleaning, Petra makes small talk with Eren, cheerfully noting the disconnect between the image of Levi that the public has, and what the man is actually like.
Later that day, while the squad discusses the upcoming expedition, Hange arrives and Eren asks them to explain their experiments with Titans.