Girls are more vicious than boys. It would probably turn out quite grizzly if it ever happened in real life.
In my experience girls can be every bit as brutal and savage to each other as boys.
There social rules are somewhat different but if you are different and outside the group you will be hounded are savaged until you either driven away or somehow manage to fit in to the group or become a member of another group that offers some protection.
Loners are not tolerated unless they are strong enough to defend themselves.
The human animal is not something you want to turn your back on; male or female.
If they made this movie I hope they got a good sociologist (and not a politically correct one) to consult on the movie. If some writer just adapted the book with female characters they probably fowled it up.
Doing some time in the inner cities studying female gangs would be helpful.