In civil society, the expected standard is not that everyone is socially and martially capable and with a razor sharp wit. Unexpected things like these generally make people flustered and confused. If a person has not faced a situation like this before, it can be very hard to come by with a proper response.
The situation is similar to being mugged, or tricked out of money. In general, the common fraud techniques work because people are not overly concerned becoming conned, and the approaches are such they work the first time because they play on the automatic responses peoples have to a situation.
Only after the fact becoming mugged people generally go through a behavioural analysis of how to recognize bad situations and how to get away from them.
In a sexual harassment situation, the initial slow response may be interpreted as a positive sign (and may erode the confidence of the assaulted party).
I'm not familiar with sexual predators but I presume the day-day activities are the same as any bullies that succeed in long careers - the offending behavior is subtle and low key, but continuous.
Secondly, making any kind of sexual proposition or advance in the office on someone you are not in a relationship with is sexual harassment.
If you are in a relationship, it's inappropriate and a conflict of interest.
Apparently around 20% of marriages begin with this kind of sexual harassment.
Actually, I believe it's not. Only if the proposition is unwelcome it is unlawful.
So if this guy hasn't been fired, it's likely that the investigation concluded it wasn't a case of sexual harassment.
The problem is that the onus should not be on her to show rejection signs.
'I'm sorry for mugging you, I thought you were just giving me that $50 - you didn't show enough rejection signs'
That lack of awareness doesn't excuse it.
In case of abuse, it's never the victim's fault for having "misunderstood" the situation. The person in a position of power bears all of the responsibility and is the person who should have known better.
Stop blaming the victim.
No, she is the victim of a manager abusing his position of power in order to sexually harass her. Her education doesn't get into play here.