This is a situation in which the girl has broken up with the man she's in love with. The relationship will have gone on over a long time, maybe several years. It has become an institution. It may not have quite broken up, or be in the throws of an oscillation - but the girl will be trying hard to get interested in other men. This may include not only going out with them, but also actively doing things to get interested in a particular man.
However, she finds this very difficult, and may even relate to the man she loves "I try to get interested in other men, but I can only think of you."
When a new man starts physical contact at the normal time, the girl reacts against it. Although she's trying to get interested in him, the idea of being held by someone other than the man she loves is repugnant.
She either fights him off, or she doesn't respond (which is probably worse from the man's point of view). Such advances are likely to cause her to end the relationship because she's embarrassed - she knows she ought to respond, but cannot. The embarrassment is likely to cause her to end the affair, whereas if the advance hadn't occurred she would have continued it.
If there hasn't been any sustained advances by her new man this too will worry her. She may go to some lengths to stimulate him. But this will almost certainly backfire - as she recoils from any physical contact when he responds.
From the new man's point of view, her behaviour is falling in the not allowable region of the All or Nothing Syndrome. If she does not respond to his advances, he will thinks she doesn't like him, or there is something wrong with her. He will feel baffled, hurt, and embarrassed (as does the girl). He may give her up, or both make no further effort because there us mutual embarrassment.
This Syndrome is really an extreme example of the Oscillating Syndrome - and the advice given there applies if a man encounters it in the field. If the girl appears to have had boyfriends in the past, then her lack of response to his advances is likely to be due to this syndrome, and not because she is frigid or there is something wrong with her. Look out for a special boyfriend in the past. She will probably talk about him, though she may exaggerate the time since break-up. If a girl says, "I'd never marry him" it almost always means she's thinking about it.
It is likely that this syndrome will occur as long as the girl is still in love with someone else. The aim of the new man should be to switch this off through becoming recognised as an alternative, through the Alternative Syndrome. Physical contact should be treated very carefully, back off if she doesn't respond, and let her set the pace. Otherwise she's likely to run away.