Your commercial Char cow would have a white face, in order to throw the white faced calf. Charolais are red animals that are diluted to white or tan. In your case she is probably a homo dilute, which would dilute her to white. Because of this, you cannot see the white face, as it blends right into the white of her coat.
The Hereford gene is incompletely dominant, which means, that when it is Homozygous, the animal will be marked like a hereford, and when it is Heterozygous, the animal will have a white face, and possibly the belly. There are other limiting genes that affect just how much (or how little)white an animal has.
So your cow is a Homo diluted, heterozygous white faced cow. She should throw you diluted (tan or grey) calves, that may or may not have a white face. If you breed her Angus, and you get a solid colored calf, that calf won't carry the white face gene. If the calf is white faced, then you know the animal DOES carry the gene. Generally, this should be a reasonably easy trait to breed out of a herd, you simply need to cull out anything that has a white face. It just happened, that with the white Char cow, that you cannot see the white face, because it blends in to the diluted coat.
