You NEVER mix bettas in a tank unless they are spawning. They will kill each other. They are not like mollies and guppies where they can be kept together. Please do not do this and put them together.
Betta females, it used to be said could be kept together in a sorority tank, some have had luck with a huge and very heavy planted tank with MANY females in it not just 3 or 4. But I have only known of two whose tanks lasted for more than a couple of months without the females killing each other.
The males and females being mixed is an absolute death sentence for all but the last one standing and that one may be so torn up that it will not survive. Bettas are not a fish you can make live like a regular fish, it is not in their nature for either the females or the males. I am sorry to say it just does not work. It is not the way they are made.
I had 5 females and all died except one and then she killed every other fish I tried with her, cories, otos, finally I left her alone and she finally even killed herself by jumping out of a tiny hole in the back of the tank in the middle of the night. I do not know yet how she could have gotten out that hole but she was out on the floor in the morning. I would say of the two the temperment of the females that I had was more vicious than the males by far.
Rose