Agree it is difficult to tell gender, but I also agree with ichthys that this is likely a male. I would base this on the slightly extended anterior rays of the dorsal, the lack of any pink, and your description that it is chasing the "male." Though this latter is no guarantee, as I have had pairs of both rams that did some extraordinary rough stuff back and forth.
Don't know the tank size or aquascape, but this usually ends in one being dead.