A lot of people with sororities have both live and fake plants. Sororities need to be very densely decorated with hiding places from top to bottom since bettas have to go up to the surface to breathe and many times, sleep on the gravel at night. Plants can take awhile to grow in, and most low light varieties do not reach all the way to the surface unless they are floaters like some mosses and hornwort. Replacing decor can also break up the territorial boundaries set up by the girls, and may cause some squabbling. Please keep this in mind when redecorating your tank.
Also, keep in mind that many pet stores market nonaquatic plants as if they were aquatic. Stay away from variegated or very brightly colored (with red/purple/white/yellow) plants--common pitfalls are brazilian swords (peace lily), ribbon plant (lucky bamboo), bamboo, mondo grass, and purple waffle.