Her social skills are not the greatest, and she doesn't show a lot of emotion. She tends to be quite rude, not because she’s mean, but she honestly doesn’t know how to be polite. She’s quite the curious girl and asks a lot of questions, not knowing when to stop. These questions can be particularly probing because she just doesn’t understand people. If answers aren’t given, she will not hesitate to spy on people to get the truth herself. She means no harm in doing this and doesn’t get why people see this as strange behavior.

Voice Reference - Justine, Persona 5

https://www.youtube.com/watch?v=6E7vtLvj7yM&t=82