Back to trifles ,You don't pronounce the S in Marans. Found a french youtube site they pronounced it like murrahn soft a and no S sound. That is just for spelling it when written. So unimportant.
She might not know the sex but she did know the breed. Do not go back to her. If you like to support a chicken welfare system you can separate the cockerels now and as long as they don't see the hens they won't fight. Actually I think one rooster and three hens for most breeds is a poor ration...