Males when immature will look very like the females, neither sex will colour up properly until settled and more mature. The males dont get their spade shaped tail or elongated pointy top fin until they grow.
Best way to tell is the females are smaller - have a rounder belly and the colour on their top fin stops and is transparent for the last quater. Also the end of the top fin is more rounded, whereas the male will have a slight point which will exaggerate with age.
I seem to be the only one who thinks it's a female. If you look at her stomach, see the dip that it has? It makes a sharp arc to the tail, which makes me think it's a female. Only time will tell