It's clear to me her approach is too rigid. I think this is partially a function of the languages she's studied: Old English is strictly theoretical, we don't really know how it sounded we can only guess. And French... my experience with French is that it's often taught is a very dogmatic fashion, with tremendous emphasis on correct pronunciation (since an incorrect pronunciation offends).

I think you're right about this. I read English and German linguistics. Both are foreign langugaes to me. Nevertheless, even our English and German proficiency lecturers were always adjusting the stuff they taught to actual language usage. They regularly updated their textbooks. I think that even prescriptive linguistics should take actual language usage into account.