Are you aware of her above-mentioned, philosophical theories?
Adding Ayn Rand would help balance the gender disparity, as well, and yet they don't. The resistance to accepting her as a philosopher is just that great.
In order to understand the problem of her popularity among philosophers compare her to someone else who was influential in having written philosophy, plays and fiction, and also for having had some political influence: Jean-Paul Sartre. Imagine Sartre's position in the canon if his writing was not Nobel-prize quality and was - let's be frank - pretty bad, but he was still in possession of some political influence, somehow, as a public intellectual. Under those analogous circumstances, I'm not sure we'd even know who he was here in the United States.
Personally, I don't feel there's little if any novel thoughts in 'Objectivism.'
For me, the thoughts of predecessors that she builds upon (or amplifies) benefit from her clear, practical, and direct writing style. She draws out implications and essentializes a bunch of philosophers—having read the original works, I can appreciate what she brings to that particular table.
In my opinion, her most significant contributions are in epistemology. I've never seen her theory of concept formation anywhere else, for example. Her grounding of abstraction in concretes sidesteps many of the issues that led Hume astray.
If anyone's interested, I can provide several books that explore her epistemology in great detail and really shine a light on her contributions.
(Her ethics is also unique, as is her politics, but I think history will look most favorably on her epistemology.)