Yes you're correct! I mentioned this but the main reason why people want only males other than breeding projects is the infamous kok. My female has a big kok for her size and age as well but this flowerhorn looks male.Yea everytime In my experience if there is a dorsal blotch it is a female. 9 out of 10 times. If it's a female you are lucky if you want to breed her. I will buy it off you lol. Why do you want a male so bad?
I have a female with a similar sized Kok. "It must be a male to carry on the Kings name". Hahahahahahaha!
The dorsal says female. Her laying eggs would be the best indication.
Vent ?Pull the fish out and vent it. Take close up pics of the vent and post pics. Only way to be sure. Make sure you have good lighting too lol. Or you can just wait and enjoy him/her until you find eggs.