well that is not how Prince Consort works out whether if Stale isn't gonna be chosen as Pride's future fiance or he eventually is.. it was just a mere hypothesis if Pride can possibly marries Stale. She only does later explained a confirmation to their marriage customs in general to Tiara.
The "almost" useless character imo was Tiara I'm afraid, because her only role came from flashbacks when Pride used her imagination of Tiara—the game heroine as a reference or guide of what she's doing. And Tiara is more NPC for acting like as a cute little sister. I want her to engage more but...
I don't think Rosa and Vest are "adoptive" relatives, similar to Stale and Pride, I don't see where did y'all get that sort of information. Maybe step-siblings from different mothers or fathers. But they're officially blood-related siblings where Vest is actually the younger brother of Rosa.
She can predict other people's future tragic events but not their minds. She's not a mind reader to understand how other people still thinks of her when she has fallen from her grace. And other people stands with her like Arthur, Stale, Tiara and Val would still find a way not to fall from her...
They can't help where atm they are so obsessed and fawning into her which is everyone who is trying to get her and win her attention like CRAZYYYY are heavily yearning her presence or existence.
You're not disremembering.. but the latter was false, a love interest or any NPC in the game won't ever become a reincarnator or a player like you said.. it doesn't have the same configurations as Hamefura.