What a sorority actually asks of the keeper
Female bettas are calmer than males, but they are still bettas: territorial, opinionated and perfectly capable of injuring each other. A sorority is not a way to keep several pretty fish cheaply in one tank; it is a managed group that you observe every single day, especially at feeding, and it can unravel weeks in when one female matures, falls ill or simply decides the whole tank is hers. Go in only if you find that management interesting in itself and you can house the fish separately if the group fails. If what you want is a peaceful community, a single female betta with calm tank mates is the honest better idea.
The conditions that give it a chance
Numbers spread the aggression: keep at least five females, ideally more, and choose young sisters that were raised together where you can, since familiar females with a shared history usually settle faster than strangers. The tank should be long rather than tall — twenty gallons is a sensible starting point — and planted so heavily that a fish can cross it without being seen end to end. Tall stems, broad leaves and floating plants break sight lines at every level, and each female needs a defensible patch of cover. Add all the females at the same time, ideally after lights-out, so nobody owns the tank first. Feed in two or three spread-out spots so the boldest fish cannot guard the only food source.
Reading squabbles versus real bullying
The first days bring flaring, sideways displays and short chases while the hierarchy is negotiated, and a stable sorority still has small daily reminders of rank. That is normal. Failure looks different: one fish with repeatedly torn fins, a female who hides all day and dashes out only to be driven off the food, stress stripes that never fade, or a single aggressor who patrols and ambushes rather than holding a patch. Judge by condition over a week, not by one dramatic evening — but do not explain away a fish who is losing weight and living in the filter corner. She is not at the bottom of a healthy order; she is being persecuted.
The honest risks and the backup plan
Even a well-built sorority carries real risks: stress lowers immunity, so disease can move through a group of closely related, closely housed fish quickly, and a hierarchy that held for months can collapse overnight. Never add a single new female to an established group — she becomes everyone's target — and never keep a male in the same water. Before the first fish goes in, own the exit plan: a cycled spare tank or a store willing to take returns, so a bullied or bullying female can be separated the same day you decide, not after a weekend of damage. Separating a fish is not a failed sorority; refusing to is what fails the fish.
Managing the group day to day
Day-to-day sorority keeping is mostly pattern-spotting — which corner has a new owner, whose fins changed overnight, who is gaining weight. When a chase looks different from yesterday's, put a follow-up question to KinsLe's Kimmy; she answers using the KinsLe Answers library.