This isn't aligned with how they meet in the Marvel comics, but we know Parker basically sells access to his soul in exchange for money and power. When Riri shows up at the pizza spot to fight The Hood,

The Marvel Cinematic Universe is in need of a genius inventor. Following Tony Stark’s death in Avengers: Endgame, superheroes are lacking tech. And in a world with magic, Hulks, and various gods, even Earth’s most powerful guardians need all the help they can get. Thankfully, Riri Williams (a.k.a. Ironheart) is ready to step in.

Ironheart has a lot of things going for it after three episodes, but there are also a few aspects it needs to work on.