Even if it's a word that she "hears all the time", it may be that she's never made the connection between the word she's read and the way people say it.
We have this discussion often at work -- a word comes along that someone has read a lot of times but never heard pronounced, and it turns out to be significantly different from what is in their head.
I had that problem as a child with a few words, and they still annoy me because I felt stupid not knowing how to pronounce them. Little Lord Fauntleroy, for example, was "fon-tul-roy" in my head, not "font-luh-roy", and worse, my mother thought it was funny. I never did go back to the stupid book.
And I just found out a couple weeks ago, watching the Moomintroll movie on TV (who knew there was a movie of that, anyway?), that I had "ululating" entirely wrong. There's another word that escapes me at the moment, though I usually remember it with disgust, that people laughed at when I said it wrong, and it sticks with you.
It just comes from reading more than you hear!
