She was 2.5" in that photo, and unforunately only lasted 2 days, she developed a swim bladder infection. She couldn't hover/keep stationary, and kept floating to the surface which was stressing her out greatly. I spent about 3 hours holding her in my hand nursing/trying to calm her, and every 1/2 hour trying to work some bubbles out. It eventually just became too much for her. That was a tough one...
Two more clues would be the 'edging' along the trailing fins above and below the tailfin. Queen's have a complete blue 'outline' where Blue's typically just have partial blue, usually completely along the top but not coming down, and just a bit along the very bottom.
https://www.saltwaterfish.com/site_11...84_61_4_4.html
The other clue is the crown, or at least circular area on the forehead where the crown with form on Queen's that Blue's do not have.