Sarah is a size shifter. Meaning she can grow to unspecified heights or shrink herself.
Because of the macro war 150 years ago all sizeshifters
wishing to live among normal size people are required by law
to wear size regulators. Macros can have them disguised as
jewelry or other accessories.
Sarah got hers modified to look like her favorite Sega character Shadow.
While she's obedient to the local authorities she tends to bend the rules.
(I'm not an artist.)