Alex Pierce and her adopted sister Blake Del Ross go to Westside High School. Alex is a badass to put simply. So most people don't know why she sticks up for Blake who's mute.
Everyone doesn't know anything about the two girls, other than the obvious. Like how Blake was adopted, how Alex and Blake's mom died a few years ago. Or a main one is how they disappear every so often and when they come back Blake is stiff and wary, and Alex has a slight limp and a bruise on her jaw.
No one questions them because they are two scared of Alex. When the new kid Chris comes and doesn't listen to the other kids, she mostly gets punched. Until she earns their trust forever.