Saoirse is described as the levelheaded member of the group as opposed to Eren's stubbornness, Mikasa's recklessness, and Armin's timid nature, but is not above cracking jokes and spending leisure time with them. Due to her parents' teachings, she is one that firmly stands by her beliefs and won't hesitate to speak them out when necessary. While she's an easy person to approach, some people (including Eren) are often put off by her directness -- in which she can be considered unintentionally insensitive at times.

Her decision making is rather confusing, but is best described as "down-to earth". While she thinks Eren is being too idealistic, Saoirse doesn't agree with others' statements that humanity doesn't completely stand a chance against Titans; showing that mostly acts on what she views as intermediate. Not only does this cause her to be ousted by some others who disagree; but she is clearly outspoken about it to the point she is unintentionally shoving this logic down others' people's throats.

Despite her outspoken and pragmatic tendencies, Saoirse is passionately loyal to the people she cares about. Due to the past trauma of seeing her father die in front of her eyes, she makes it so that she uses logical means to protect them, and frequently puts them first before herself. Her fierce loyalty occasionally clouds her judgement, however.

As the series goes on, Saoirse learns to consider others' feelings first and choose a side; as well as learning to take care of herself as much as she cares others, and trust that they can take good care of themselves. During the timeskip, Saoirse seems to have retained her levelheadedness and pragmatic nature, albeit less loyal than she was eventually because of numerous events that led them to dying /nearly dying when she put them first.