Answer

In her books (like everyone else, I read them in my teenage years. They’re written decently enough, but they’re very pathetic—that is, full of excessive pathos. Her characters are portrayed like ministering angels) there are mainly two themes: self-realization and autonomy. Those two are not equivalent to egoism, and as for them, I’m completely in favor. But regarding her egoistic thought (which I don’t know in detail, although of course I read Moshe Kroy, who took it to the extreme), I’m very skeptical. My feeling is that she underwent a kind of repentance process, and so she reached an extreme. They say that someone who at 17 is not a communist has no heart, and someone who at 23 is still a communist has no head. She went through the first stage, and indeed overcame it and left it behind. But then she went out to the opposite pole: extreme individualism. Like every pole, it is extreme and mistaken. That is why there is such pathos in the description of the characters. Like any penitent, she describes her current world in glorified and perfect terms.
Many assume a descriptive-factual premise, according to which a person acts only out of egoistic motives (I disagree with that. See column 120). According to that premise, the discussion doesn’t really arise. An egoistic doctrine only tells a person: don’t deny what you are, and don’t repress it. In any case, you act only for the sake of interests.
But one can reject that premise as a factual description of human beings, and still advocate it as a value-guiding way of life: a person should try to act egoistically even if he wants to do otherwise. That is “rational” egoism (more accurately: rationalistic. Not rational at all). In my view this is simply nonsense, and I see no need to grapple with it.
Moreover, in my current lectures on morality, faith, and Jewish law, I elaborated at length in explaining that even if a person acts for the sake of the satisfaction he gets from being moral, his act is no longer a moral act. It has to be done with no interest whatsoever, material or psychological. One should do the truth only because it is truth (Maimonides, beginning of chapter 10 of the Laws of Repentance).
Therefore, a conduct of rationalistic egoism is basically telling us: do not behave morally (that is, only negative morality—not to harm others—and not positive morality—to help others and take them into consideration). So your question is, in my eyes, equivalent to asking whether it is proper to behave morally (including positive morality). My answer: yes.