At first it seems that Addy showing up is unrelated to Bella being smart - then you realize that the Volturi only met Addy because Bella informed then about Joham and hybrids, which caused Addy to join them.
Allirea's power explain's why hybrids are completely unknown.
Kind of a meta example, but I've heard complaints about Luminosity's Bella being too... clinical, too formal in narration and while I don't mind it, it is kinda true. However, I also noticed the narration gets less formal once she's a vampire. This makes sense if you realize, based on the prologue, that she's telling the story from memory after the Volturi attack on La Push. The reason the human!Bella section is more formal is because she's telling it from vague human memory and memorized journal entries, whereas the vampire section is more natural.
In Luminosity, Allirea's state of rest - what happens when she's not actively exerting effort - is to be unnoticeable. This has always been the case for her. Anything that is clearly "about" Allirea is not worth notice unless she acts to counteract that default. She's also a half-vampire. This means that her mother died an agonizing death by childbirth. And no one cared.