Don't you think, if you don't know the gender of your fish, that you should not breed? I just read a thread and this person had the "female" ready when the "female" started blowing bubble nests and stuff. Even though this is a male for sure.
Some females do blow bubble nests, and some males have a fake egg spot. But who knows, this person could know a lot about breeding Bettas, just not as much about Bettas themselves.