Really?! I missed it, when did it reveal that?!
I think its the time of the back ground check. It would be impossible not to get that very important information
Maybe her father once told the prince that he had a daughter
He always treats her like a girl. He's flirty, handsy when she permits it, and is always bringing her presents to impress her. He even refers to her as "she" and "her" in personal thoughts. He wouldn't be doing any of that if he believed she was a guy.
Not to mention he was hella jealous and possessive when someone else tried to get her to marry them. That's not the reaction of someone in a "bro-mance"
Naw just the last chapter confirmed it. She realized she had been undressed by the prince when she fainted, then assumed he didn’t figure it out somehow because she’s a dumba**. Cue next panel showing him all fluttery and ready to propose because he undressed her and duh figured it out. X-D
Okay, ty ヾ(❀╹◡╹)ﾉ~
The fact that she hasn't figured out that he already knows is ridiculous