Seems like Norn did read nearby every situation in regard of Rudy wrong....
Also seems like Rudy completely ignored Norn while in Millishion... Should have been socializing with her after he made up with Paul.
Man, it's harder because it's relateable. Not really that far up fantasy problem, and I can understand why Norn can think it that way in her perspective.
Norn is just a kid, people tend to forget, that's what kid does especially when they encounter scary stuff or bad person (also misunderstood person), it's etched on their mind, her father is all she got as well after the incident which took years for them to even get their semi-normal life back
Also, she didn't actually know how her brother actually are on top of her memory of him when she's even younger and seeing how Aisha interact with Rudy, she thought that maybe Rudy is avoiding her instead of trying to mend things with her since Rudy is also being timid