It's hard to believe that someone as smart as O'Reilly could be stupid enough to keep after a female after one or two rebuffs. It's also strange that she just didn't tell him after one or two advances that she would press legal action if he didn't desist. I speculate that she didn't rebuff him. She may have even "smiled" or "unh-huh'd" from time to time, to make him think she was at least listening. My guess was that her motivation was to either get money, or bring him down a peg or two. Dislike and hate are powerful motivators for some people.
IOW, I don't think this is about the money. This is about power, and she is trying to assert something over him.
There is no doubt in my mind that this woman has tapes. She either has tapes or a screenwriter. Way too many details. As mentioned upthread, she could have been just recording along, being coy, and thinking that she was going to get rich off this stupid lecherous bastard.
That being said, O'Reilly needs to be taken off the air. I will never look at a loofah the same way again.