From a meta standpoint, the fact that Raina repeatedly portrays herself as a flawed and sometimes selfish teenager rather than as a paragon of virtue (note the whole Sammy incident). It makes her character arc more meaningfully, and it's pretty damn brave to admit that you aren't perfect.
Raina, Amara and their mother during the Loma Prieta earthquake. This is one of the largest earthquakes in San Francisco history (magnitude 6.9) yet they don't panic, immediately hiding where they know it's safe to do so.
The little moments where Raina stands up for herself against her friends. They're easily ignored, yet it's clear through the excellent artwork and subtle expressions that their "jokes" aren't all that funny to Raina.
Sue (justifiably) going apeshit when she learns that the periodontists who are supposed to clean up Raina's badly damaged gums basically did mouth surgery without laughing gas or novocaine. Up to this point in the book, Sue has been very laid-back and mild-mannered. Goes to show how much she loves her children.
Dentist: Well, we did a quick cleaning of the gums, and I guess we didn't wait long enough for the novocaine to work, and we could have given her laughing gas, but we didn't think she'd need— Sue: WHAT?!!YOU DIDN'T THINK TO ASK ME IF ALL THAT WAS OKAY FIRST?!? Employee: Ma'am, please, the other patients will hear... Sue: I DON'T CARE!MY DAUGHTER JUST FAINTED, THANKS TO YOUR NEGLIGENCE!! Let's go, Raina... and we won't be coming back. Raina: ...That was pretty awesome, Mom.
Raina: I can't believe you guys. You expect me to laugh off getting pantsed in the courtyard? Kaylah: No, but- Raina: Forget it. None of you guys respect me. I've had enou- (runs into Nicole and Karin) Nicole: Hee hee! Uh, hi! Raina (thinking): Don't start crying... Don't start crying... Are they still waiting for me to start crying?! Raina: You guys want a reaction from me? Fine: Karin, I am not a dog. Nicole, I am not a vampire. note Nicole called her "vampire girl" in their 6th Grade yearbook. Kinda shows how much that nickname stung since she still is hurt by it three years later. . Nicole: Oh, c'mon, I haven't called you that since- Raina: NO. And I am not going to let the rest of you disrespect me anymore! I'm done. Good-bye.