This character exists primarily within the Sonic Boom continuity.
Information in this article may not be canonical to the storyline of the games or any other Sonic continuity.
The Rabbit Girl is a character that appears in the Sonic Boom television series. She is an anthropomorphic rabbit and the Rabbit Girl's counterpart from an alternate dimension where Sonic never existed.
The Rabbit Girl is essentially a doppelganger of her Sonic Boom World counterpart and is so identical to her in both anatomy and attire.
At some point, the Rabbit Girl starred as an actor in a commercial for Knuckles' Upper-Body-Only Workout Center.
Somewhat archaic, the Rabbit Girl seems to like manly and macho men.