I bought a new betta today after I did something horrible to one of mine I was about to put into my new sorority tank (when I was putting her into the cup, she fell out of my net and down the sink drain, I cried for hours because I couldn't get her out, and feel absolutely horrible about it, please don't judge me)
But I went to petsmart to get a new light for the sorority tank and was looking at betta females to possibly add, I found one labeled as crown tail, but was a double tail, the CT females were on sale so I couldn't resist buying it (also I had been looking for one to breed to improve finnage) but anyways, it was labeled as a she and I'm starting to think it's a very young he. It's fins apreminger than any of my other females and I can't see an ovipositor, but it's still a decent amount smaller than most of my females so I'm unsure.
Can you please post pics of your double tail male or females OR help me figure out another way to tell??