No, female bettas would not be okay with firemouths or a red fin shark. The firemouths and shark are WAY too aggressive for betta girls. I have two in my 55gal community with one angelfish (about 3" long) and they do fine because there's tons of space in the tank.
I'm not sure if you're aware, but breeding bettas is a time-consuming and expensive process. You first need to start with good breeding stock (not cup babies from Petco or Petsmart as they have unknown histories and could carry genetic disorders). You will need a large growout tank (30 gallons or larger), plus at least one hundred of 1 quart growout jars for the males once they get too aggressive to be housed with the females. You need to do daily water changes on the growout tank and on the growout jars (100% changes in the jars). When trying to get your male and female to mate, you must watch them constantly because there is the possibility of your male killing your female (or even vice versa). You also need to remove your female as soon as she is done dropping eggs or the male will attack her to defend the nest. The male must be removed from the tank as soon as the fry are free-swimming so he does not eat them. You must condition your bettas with live foods and a varied diet before breeding as they will not eat while breeding and it takes quite a bit out of them (the female especially). The male will not eat until after he is removed from the breeding tank, which can be up to five days after the eggs are dropped. I know someone who breeds champion bettas that consistently win at IBC conventions and shows (in fact, two of her halfmoon bettas from her most recent spawn picked up best in show female and best in show male at the Connecticut show this past weekend and one of her other males picked up best in show at the Florida show a couple weeks back) and it is her full-time job. That is all she does.
