very sorry. It sad. I would afraid to have sorority it a lot of risk i guess. I just was talking to someone who's betta died and she has 10 gall. I gave her idea about sorority but i also told her that it can be risky. You never know with this girls. Some of them can be aggressive like males are.
I am very sorry i hope your other girls will live in peace. But i guess you have to be ready for anything with them. And have extra tanks like i saw someone recommended in case you have to isolate them.
Good luck .