In addition to the above advice, just a quick caveat. I would recommend checking several style manuals just to be sure she doesn't have any leg to stand on. You may find that she is using a reference that is in disagreement with the way you believe the word should be capitalized. I have consulted several editorial style references about particular issues in the past, and I've gotten different answers (so I chose what I liked best). It is hard to say there is a "gold standard" for most things. (But then again, if it's a very obvious mistake, you should be able to bring in several references saying the same thing.)
