That particular line of attack against Rand is old and tired. Like, more than 50 years old and tired.
Do Rand's personal rape fantasies come through there a bit? Perhaps. But it's not necessary to psychoanalyse Rand to get clear of the rape problem there.
The easy path towards refuting that attack lies in the fact that Dominique engineered the situation and was completely in control. She knew when she ordered him brought to her house what services she expected him to render there. So, while the passage may have been written in the manner of a rape, there's no doubt that it's actually consensual. The reader knows that when she was watching him at the quarry 12 hours earlier that she had made up her mind how the evening would progress.
There is, I think, an even more important refutation. Rand's stated goal in writing the Fountainhead was to create a portrait of the perfect man. Howard Roark is an archetype, a true creator who builds purely for the love of his creativity, and is genuinely unconcerned both with others' opinions of his work and with the materialistic rewards that it might bring him. Nobody in real life could be so genuinely perfect. All of us, no matter how much we love our work, and no matter how much we might pretend not to care about externalities, really do give in at times either to the socialistic sin of caring about the approval of others, or to the materialistic sin of caring what baubles we might receive for it. Rand knew this. In creating this perfect but fictional man, she had no illusions that anyone in real life would ever achieve such a status, although we might strive for it.
So, in giving herself to Roark, she is not giving in to a real-life man that might actually exist. She is surrendering to an ideal, an archetype. Compare to the story of Leda and the Swan. There too, although some versions portray a rape, the most important interpretations see Leda as knowing that the Swan is Zeus, and willingly copulating him for that once-in-a-lifetime opportunity to to get something beyond the capability of mortal men to provide.