This is Sally Acorn, princess and leader of the Freedom Fighter rebellion in the Sonic SatAM cartoon. Here's her story:

Animals are living happily on the planet Mobius under the wise rule of King Acorn. His daughter Sally and her friends are getting along great! Everything is well until Dr. Julian Robotnik, King Acorn's war minister, decides to rule the world with an iron fist. He uses an invention by Sir Charles 'Uncle Chuck' Hedgehog, Sonic's uncle, to get his way.

You see, Chuck invented something called the Roboticizer that would turn a living being into a robot. This was supposed to be used to let people live longer once their natural bodies wore out, but there was a glitch: roboticized people lost their free will. Robotnik used this to his advantage and staged a takeover of Mobius, enslaving the population and sending King Acorn into the void. Young Princess Sally and her friends escaped, though: to a hidden village called Knothole. There they grew up and started plotting a rebellion against Robotnik.

Sally is the leader of the Freedom Fighters. She is responsible for rallying the troops and making the plans on their raids of Robotropolis, Robotnik's capital city. With Sonic and their other friends, they go on missions to bring the roboticizers and power plants offline temporarily: anything to disrupt Robotnik's operations. They're also working on finding a cure for roboticized Mobians, especially since Uncle Chuck is one of Robotnik's drones and one of their fighters, Bunnie, is partially roboticized.

Robotnik and his servant, Snively, are the main humans Sally has seen, so she is liable to deeply distrust any human being.