From your description and the images, I would say male. For sure by 4.5" a female would have solid, dark colored pelvic fins. If you don't see that, it's a male.
I can faintly see the area in the first half of the dorsal where it will either be dark coloration or blue coloration, and I do not see a lot of blue spotting in the unpaired fins.
This female is around 3.5" and you can see how the front dorsal is darkening, spangled are disappearing from the tail, and pelvic find are going dark.
Your fish would already show these traits if it was female at 5.5" in my experience. Males don't really color up much different than juvenile unless they are dominant or spawning. Is this fish dominant?