Halfmoons fins are much longer than a plakat. Plakats have the shortest, stubbiest fins
Female veil, plakat, half moon, delta, crown, dumbo, etc. can all look alike.
The only true way to know is to know your source.
I had/have female half moons that look like male plakats, half moon males with egg spots and plakat looking shorter tails, and females with almost full beards and blow bubbles, just to add to the confusion.
Bookmarked this a while back when I had the same question. The rays on the fins are sometimes very hard to see and not always easy to do (or even possible on some colors) but the rays on the fins should usually tell you what type she is.