Joanne Garfield is Lauren's BFF—
Oh, wait. Scratch that second F.
Joanne is Lauren's best friend in Robledo before all the big changes happen—before the Garfields move to Olivar, and before the neighborhood is destroyed. Joanne kind of gives our prodigious Lauren some normalcy, some ability to just be a regular teenager a little rather than some super genius out to found a religion. Of course, Lauren doesn't really want things to be normal, so she pushes Joanne to see life from her perspective. And we all know how that ends up.
Let's get some basic facts on Joanne. Her boyfriend is her first cousin Harry Balter (4.28). She's white (4.28). She's scared of dogs (4.46-49).
So, yeah. That's Joanne.
The big incident everyone remembers is Lauren's attempt to make Joanne see the importance of change. Lauren's got a point, but she scares everybody when she talks about how the neighborhood is becoming increasingly dangerous and how it'll eventually be destroyed by attackers. Lauren recommends that she and Joanne learn how to survive, but Joanne dismissively sums it all up as "we learn to eat grass and live in the bushes" (5.136). Then she tattles on Lauren, telling her mother that Lauren is loony tunes (6.1-4). Gee, thanks, Joanne. What a big help you are.
Eventually, Joanne and Lauren kind of patch things up, but it's not long until the Garfields decide to move to Olivar, hoping the company town will give them a brighter future. Poor Lauren, so very friendless.