It is not a good idea to keep multiple female betta fish in the same tank. Although it is possible to do so under the right conditions, the fish may still fight with one another.
Female bettas may only be placed in the same tank if certain requirements are met. These include maintaining a proper plant environment and using a tank of adequate size. It is also important to keep an eye on the population of fish within the tank. Female bettas can be just as aggressive as male bettas at times and will attack other females that resemble themselves regardless of species. If they are placed together, female betta fish must be monitored closely for signs of aggression.