Re: Where has she been living?
You've been working in computer security for years, but you're not aware of threat models, partial trust, transitive trust, trusted third parties, or any of a dozen other security concepts that include some trust aspect?
Engineering is impossible without partial trust. "There is no such thing as 'trustworthy'" is a naive ideological statement, not a useful position for security engineering. The first lesson of "Reflections on Trusting Trust" (and more formal studies of trust in systems) may be that every component is suspect; but the second is that it's impossible to get anything done without assigning trust relationships throughout the system.
Rutkowska - a serious, well-known researcher and developer - is perfectly aware of all of this. Her point is that mainstream OSes are very liberal in their definitions of trust boundaries, for example in broadly assigning all processes owned by a given user into a single trust domain. Qubes (which has been available in some form for five years) is built around a more pessimistic trust model, and that's what Rutkowska was generalizing in her Black Hat talk, as far as I can tell from the article.
And yes, obviously it's not a silver bullet, because there are no silver bullets. That doesn't mean it's not an important contribution.
Trust in operating systems is a very complex and difficult area. Reducing it to a slogan is a pointless exercise.
 Something I'd kind of hope a practitioner of IT security would know. Following research in the field is important.