You are quite right. Though libertarianism existed in previous incarnations (such as classical liberalism), Rand was the first one to embody her political principle into a single statement that libertarians tend to accept as their modus operandi. That principle is known as the "non-aggression principle". Some libertarians also call it the ZAP, or "zero-aggression principle".
Objectivism is far more than libertarianism. While Objectivism is a full philosophy dealing with metaphysics, epistemology, ethics, politics, aesthetics, teleology, etc. etc., libertarianism is politics-only, shared among those of many different philosophical roots, even Nihilism. The primary reason Rand didn't care much for the libertarian movement as a whole is the fact that it didn't have her ideal philosophical root.
As an Objectivist I would agree with her Of course, I am a member of the LP anyway. I don't see much choice.
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Bump of the year.