And it doesn't take a Rasputin-like figure to be an abuser. Plenty of people are taken advantage of and taught to believe things they later realize were abusive, even in relatively short situations. Pretty held all the power here -- he controlled where she was staying, he helped her get to the conference, she was intoxicated, she believe he was her mentor, she believe he had the ability to get her industry connections, etc.
Coercing someone into sex that they later realize wasn't consensual (once they are free from that person's influence) doesn't mean she was lying in the moment or is somehow "discovering" something now.
> Can I not expect her to know, in the typical case, whether she does or does not consent to sex?
Adult humans (because I think this can happen to men too), can absolutely be caught off guard and be "unsure" about whether they are consenting to sex. Not everyone is wired the same, and not everyone is able to make a quick snap judgement. Not everyone is fully able to say no when pressured.
Furthermore, grappling with the question, "Was I just raped/sexually abused?" is really, really challenging. What does that do to your identity? Are you forever a victim? Are you going to have to out yourself and someone else? Will you forever be the target of the public's pity? Are you going to have that stigma attached to you when you want to enter relationships in the future? That's a LOT to put on someone, and many, many victims choose to try and believe that things were consensual, because it seems easier that facing the realization they were abused.