this is a beautiful piece on itself, but if I were to guess who it was, it wouldn't be Catelyn. She indeed looks too young, and you can't really tell she's redhaired (being that a promient feature of hers)
This is a very poor depiction of Catelyn. She looks much too young, and much too calm, after seeing her son and her bannermen butchered like meat and cutting an innocent fool's throat. She looks like she's posing for a pinup.
I really love that we've got something of Cat during this cataclysmic moment, though I have to say that she does look a bit too young, she looks more like a woman in her middle to late twenties than a woman in her fourties