Yes you can, though it doesn't always work out. You need a tank of at least 10 gallons and four or more females to spread aggression around
They usually quarrel a little right when you add them, but within a day or so they work out a pecking order.
I have 12 female bettas I got from wuvmybetta and they are all very healthy, no nipped fins or anything. They get along very well. Though they are in a 120 gallon so they have plenty of room to get away if someone turns into a bully. :]