"Sam's kind of tired today," mom explains to me, while Sam unenthusiastically tries on another shoe, scratches her thin arms, plays with her phone.
Then a call comes in, and Sam transforms - her face lights up, she takes the call, and then she proceeds, for the next minute or so, to become another person: animated, screaming with laughter, starving for gossip ("Are you kidding me? He didn't! Shut the fuck up!"), and obviously thrilled to be young and alive.
As soon as the call ends, though, mom tries to reassert herself: "Sam, oh my God, Sam, put the phone down."