Your chick is definitely a roo, no doubt about it. My 8 week old girls combs aren't even pinking up. Of course some breeds develop faster than others, but still at this age it's quite uncommon to see a pullet with that size and color of comb.
It has to be a hen. That breed of chicken has big combs, so most likely its a female. I've had MANY of those chickens and they have the biggest combs out of all of them. The comb is pinkish color, so now it's even a bigger chance of it being a hen. All my family say it's a hen, why not.