No, I didn't "hear" that one, I saw it, here! In some ways, I can't blame her. If you're a historian, I guess you're going to be able to pick out what you think are "anachronisms", "modern" thinking in historical times," etc., etc. But when it comes to things like words for "mother", "father", "mama", papa", etc., what's going on here? It's interesting that many languages have "pet" names for mothers and fathers and other close relatives, and a lot of them sound like "mama" and "papa",especially when coming out of young mouths. But Magistra et Mater isn't a linguist, so presumably she wouldn't be aware of this.
It seems to me that what she really wants, and what I've complained about elsewhere is "total" accuracy for whatever period she's reading about. Even in periods where there's an abundant amount of material that can be mined as research, this simply cannot be done. As for as "modern" attitudes go, well, I kind of wonder. If, for example, my heroes had completely "early medieval" attitudes, they would probably be totally unsympathetic. That doesn't mean I don't recognize that such attitudes existed, it just means that at least some of the people are exceptional in some ways(besides, it's "romantic science fiction set in medieval England", not a history treatise, nor a "pure" historical novel. And it has "anthropological" material in it, or I wouldn't otherwise be writing about Dauarga/Neandertals as some of my central characters.
The real problem here is, a kind of academic snobbery, not unlike some "literary critics" who moan about "popular" works like Twilight and the Harry Potter series. These people want "beautiful writing" about "character development", whereas many readers just want A Good Story. This doesn't mean you should write sloppily or have inconsistencies in your story. It just means that there are some things that are more important to a lot of people than they are to these literary snobs(there's no other word for them, in my opinion). Historical novelists, however, do offer an opportunity for the reader to learn "more" about whatever period they are writing about, and it is not uncommon for people who read historical novels to later get into history majors, and become professionals, in some way or another. Similar things have happened to some science fiction readers, who get into science that way.
I think Magistra et Mater has fallen into the common trap of thinking that, since they have become "experts", they must find fault with anything written by a nonexpert. Some fiction, like some historical films(such as Kingdom of Heaven and Braveheart in the movie realm, and things like The Da Vinci Code in the "literary" realm), richly deserves the opprobrium it is given. These pieces are laughably inaccurate, as in Braveheart, and/or they have, as in the case of The Da Vinci Code, very obviously "mined" certain dubious source "works", which are themselves full of historical "junk". However, the author apparently does not recognize that a historical novelist is not a historian, is not expected to be a historian, and shouldn't be held to the same standards as a historian, no matter how "representative" of a time or place any piece of historical fiction is supposed to be. I've seen whines about this in anthropology journals(mainly about the Jean Auel's Children of Earth series. There, the problem is, that the academics in question wish they were as famous, or had made as much money as Mrs. Auel, but they're academics, and aren't as famous as Jean Auel or her series. It is quite possible to make legitimate criticisms of her series -- she has obviously done extensive research, but Ayla, her heroine, is too much of a prehistoric "everywoman" to be completely credible. Yet, if she hadn't written Ayla this way, would anybody have eve read her books? I don't have an answer to this, but novelists must make authorial decisions all the time about things like this, whether it's "accurate" or not. On the other hand, I do think the novelist in question should research as thoroughly as they can, and work the "accurate" bits into the background. It won't be "history", exactly, but it might inspire someone, some day, to research a period on their own or even(gasp!) to become a historian themselves.