Okay, I guess I solved the Hustleverse lore now.
At least, Pizza Girl's story mode.
So Pizza Girl is the average college dropout, she didn't felt content with her life or whatever other reason there might be for her to not complete her studies. She started hustling for as much money as possible as some kind of cope mechanism, as she feels inferior to her big sister who has a stable office job and a good income and she's mainly driven by jealousy. Through a long time of delivering pizzas, she developed mad driving skills.
One day, like we see in the latest cartoon you made, she met Malice, who is a wannabe racer who works at Ihop. They become friends after a race and Malice slowly but surely starts to influence Pizza Girl to try out racing as gig, and she accepts either because there are cash prizes or she just likes it.
Through winning her races she mets/befriends various side characters, like Neon, but eventually she draws enough attention as a racer that it grabs the interest of Pris, who is the rich powerful lady who has the best car, the best job and is the best racer around. Pris challenges her for a race with a lot of money on the line. And of course, she starts scheming.
She threatens Pizza Girl that if she doesn't throw the race, Pris is gonna fire her sister because she owns the office that she works in, and that sends Pizza Girl into emotional conflict. she ditches her friends and doesn't know what to do now that she's at a cross road. She and her sister can have their huge moment of reconciling, and they hug, and it's really hot, and she rushes to the final race and arrives at the last moment.
She races Pris 1v1, she is the final boss of the story mode. Pizza Girl wins, she gets all the glory and most importantly, her sister's respect. Pris is most surpirsed and has a change of heart of sorts, not firing her sister and becoming the wild card tsundere of the group. Pizza Girl gets the huge prize money but she has to use it all to fix her car that she trashed during the race. And that's the end of Pizza Girl Story mode.
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But that's just a theory...