Whoops, forgot to check this post! XD
I've decided against adding minnows, since after I brought them home they seemed really hyper and would've probably been extremely annoying to any betta I were to put in the tank.
My two female bettas are very placid and aren't very aggressive. I can honestly say, I did put a couple of minnows in one of their tanks and my betta just ignored them.
As for the sorority rule; I am perfectly aware of having at least three female bettas. I have had sororities in the past and never had any problems with my girls. When I said, "two of my female bettas" I meant one with five of the minnows, since I was splitting the minnows into two groups. Sorry for the confusion.