Yeah, but K. Rool got a trophy as well. That doesn't mean anything.
And though, yes, she is a heroe and a female, she would still probably be a light or medium weight character. However, King K. Rool would add a villain, a heavy weight, and overall a more interesting character. I mean, he shoots cannonballs, throws his crown like a boomerang, calls down cannonballs from the sky, using a copter back etc. etc. What does Dixie do? Fly with her hair, and that's about it. Grabbing with her hair and such doesn't really count, because those couldn't really be special moves. In fact, what would her B moves be? Can't think of any? Neither can I.
K. Rool is simply more important, and would probably be more unique than Dixie ever could be. Not saying she won't ever be in, but she definetly has a lower chance than K. Rool.
Edit: And Commander Blitzkrieg, I love that anti-Geno message in your sig! It's exactly how I feel about him.