Some claims in The Secret are simply factually wrong, and so fall apart under their own weight when scrutinized. Specifically, The Secret claims that quantum physics supports and explains the "Law of Attraction". At its most superficial, this claim sounds reasonable to the uncritical layperson because attraction sounds like magnetism which is a real scientific thing, and any mention of the term quantum physics sounds scientific enough to be acceptable at face value. Who's qualified to argue against quantum physics? The Secret says that thoughts have energy, and similar energies are attracted to each other. That's their quantum physics.
In fact, scientifically speaking, that statement is completely meaningless at every level, and at no level does it have anything whatsoever to do with real quantum physics. In fact, the closest analog I can find in science is that like charges repel one another, they do not attract. But we're talking about "thought energy" here, so we've already left the realm of real science and are in the world of metaphysics. Since metaphysics is a philosophical invention with no connection to real physics, either quantum or classical, you can pretty much say whatever you want and there is no scientific way to respond to it. Thus, The Secret's claim to have roots in quantum physics is childish and meaningless, yet it succeeds because it appeals to the uncritical layperson's tendency to accept scientific sounding terminology at face value. Check out Rhonda Byrne's background in quantum physics. You'll find that she took the same university courses that your cat did.