I'm notoriously bad at sexing the RF tortoises. I've had two of them for over 2 years and they're both quite a bit bigger than yours and I haven't been able to sex them. But the Forum keeps telling me they're both girls (they look male to me, concave plastron, etc.) Yours might still be a bit young to sex, but the tail is pretty small. You can't go by the plastron because some females have a concavity.