I don't think there is any doubt that women have great capability for violence. In fact, in some ways, women are more vicious...perhaps not physically but emotionally. In my experience, women hold grudges for much longer than guys. A scorned woman will hate you forever, while a guy who gets mad at you may punch you out..but will get over it and get on with is pretty quickly.
Having said that...I do think the island would have looked different with girls on it. There would have been a softer touch. For example, (although a stereotype) women tend to be nesters and by nature...nurturing. They may have helped form "families" and established home groups if they were there...which may have delayed the onset of violence for awhile.