If Flynn on the Bumblekast says Metal has to use he/him pronouns to validate maintaining Sonic's identity, the best way for Sonic to help her overcome her gender issues would be to explain that his gender is whatever makes his partner gay (which is true - that is his gender.)
That way, since Metal's love interests are all girls, she'd recognize that to make them gay she has to be a girl, and thus, she is able to be a girl like she wants to while still conforming to the usually-boy Sonic's identity like she has to.
Everyone wins!













