I have 5 female and one male betta in my community tank, and they all get on fine with each other and the other citizens. One thing I have noticed though (through experience - we have 17 bettas in the house!) - the redder or darker the betta, the more aggressive they seem to be. The ones in my big tank are all lighter veil and crowntails. The darker reds and blues have to have their own tanks because they seem to be very aggressive, and we have had to have a few rescues.
Seeing as the family seems to be addicted to bettas, I am considering renaming our house "The Alpha Betta Place"