Lets see....oh ok so last year I put a red dragon HM in with a red copper DT into the breeding tank....well he couldn't figure out what to do...well yeah she shreded him and the rest of the time I had him he looked kinda ..."DUURRR"...maybe she caused a brain injury :P
Personally I believe that bettas are the way they are because as newborn fry the fall the to the bottom of the tank/tub head first and it causes brain injury (doubt this seriously but its nice to think it :P)...if it didn't humans would be sold in petstores not them :P
* Also to above* Females will build nests when kept alone. Soon if you put another female near her she'll flare and try to attack her to defend her territory. Females are the weirdest ones of all :)