I have two red empress, 3-4 inches (closer to 4) . The male first started to show some color on his anal fin only. It started to look tinted in some light. It was not red and in some light still looked clear. Then it developed three small orange dots on its anal fin. Stayed that way for a month or two. Next it got a very small amount of irredecent blue on its lower jaw (again only visiable in certain light at certain angles) It has been 3 more months now and it is getting very red fins and tail and bluer head, its body still has the least color development but i see changes there too. Watch the anal fin and jaw. The dots or speckles on the anal fin are so tiny and light colored it is very hard to see at first. I saw mine by taking a close up of the fish and cropping it to blow it up LOL. I could see it in some pics . Those two areas will be the first to color up. The female has clear fins. (When small still the male and female body will look identical except for the anal fin on a changing male) No spots or darkening/tint look on anal fin for females, no speckles that look like tiny egg spots when they first show up.
Here is a pic of my male as he was just starting to show color on the anal fin and not much else (he stayed this way for quite awhile) 2-3 inches
Here he is several months later still developing (very slow rate of color development) 3-4 inches
He is now all vivid red fins and blue head, over 4 inches and getting more colorful everyday. Still not done changing, but getting more color. Sorry i dont have a current pic, i can try to get one if you want and post it this week if you want. Let me know.
About the female dominance thing. I found mine as juvies were equals, as they matured the male became more dominant , the more he colors up and develops the more dominant he gets over her. It is possiable the fish is a male and is interested in the other fish as a breeding partner. The other option is the redempress female is larger and can bully the smaller other breed. Since i dont know the fish i cant tell which is more likely.