there are some people who keep a trio of grrl-Bettas with a single Betta-boy, but they know what they're going. i learned the hard way when my girl Virginia was torn up by my boy Donny, who is oh-so docile and didn't even attack the invading Mackenzie when he leapt his breeder-trap wall.
watch the grrl-Betta, if she's being aggressive to everyone in the tank perhaps you could consider moving her into her own tank until she calms down, then be very careful and introduce a cleaner-fish and see if that works. otherwise you might want to invest in a nice small tank for the Betta-boy, as i've heard Bettas and Gouramis don't always agree with each other and you could end up with a chewed-up Betta and a chewed-up Gourami. either way, it's a good excuse to get another tank
and, since you're interested in breeding Bettas here's a teeny bit of info i've gathered from about ten zillion forums, books and sites. let the male build a biiiig bubble nest, and keep a seperate tank with 1-3+ females. pick out the female you want to breed him too and condition her OR condition all the females and pick out the fattest girl. introduce her with a covered breeder trap and wait a few hours, then let her into the tank. make sure there's hidey holes! the male and female will be nervous, but let them dodge around and nibble a bit, but not enough to damage the other. keep them there for 24 hours, if they haven't bred remove the female for a few days and try again later, if they do spawn remove the female and put her in a hospital tank to recover, and let the male raise his eggs, unless he starts snacking on them of course
i think that's accurate enough... please inform me if i've made a stupid xX