My wife used to keep & breed Bettas (B. splendens), she loved her 10gal with her
'Girls' more than all but the finest show quality males.
Females can be every bit as aggressive as any male, they can do fine for a time and then WHAM!, two of'em decide they hate each other...
All par for the course, these are a decidely belligerent species.
We found that 5-7 females in a well planted 10gal was ideal so as to spread out aggression, more or less just seemed to be asking excessive trouble in a 10gal.
Regardless, sooner or later there is trouble, no ifs ands or buts about it. :Evil:
You just have to expect it and deal with it.
Females flair at each other, at males and at anything they have a aggressive reaction to.
Some females are just psychotic and need to kept in solitary, not even suitable in a semi-aggressive community with fish of similar size
If your getting any wild anabantoids, e.g. plakats or etc, mixed in with run of the mill/mass bred Betta splendens something is very funky.
You may find some males culled as females due to lack of finnage, trouble can brew very quickly if these get put with either male/female companions.
Wilds (B. splendens) females bear little resembelance beyond basic body shape and finnage to our commonly marketed female Bettas.