Before I go off this is not about anyone specific, I've come across more than a handful of people doing this and to be honest it's getting to me.
YOU DO NOT PUT A MALE AND FEMALE TOGETHER IN A COMMUNITY TANK!!!
If your spawning then yes by all mean put them together, but NOT in a community tank, or any tank no matter how heavily planted you think you have it.
I saw too many posts last week (and it seems to be continuing into this week) about people saying their girl betta is sick but on the "tank mates" part of the forum they have "a male betta..."
to quote Mythbusters "Well there's your problem!
And no you cannot just divide and have everything be better, the hormones and pheromones released into the water will still stress the heck out of your fish! Females will still get eggy, males will be on guard looking for her.
"I can smell you but I can't see you."
the only solution for houseing males and females together is SEPARATE
Please people do your research before just throwing them together.