I'm confused about Katharine.

[deleted]

Women do crazy things when they fancy you.

I think there was just a lot of tension. Obviously he was trying to push her away from him which wound her up - Remember the scene where she tries to initiate conversation in the truck, and he basically tells her to shut up - he got under her skin.

Of course this anger just made her passion for him stronger. Once she had got the violence out of her system by slapping him she submitted.

Your theory may be right too, she was probably feeling a lot of guilt and it was almost saying "how dare you drive me away from my husband".

It was a very complex affection.

It has nothing to do with women doing “crazy things when they fancy you.”

K and Almasy are very intelligent characters who fully understand the implications of what they are about to do; they do not take it lightly. In all their scenes leading up to this scene we have seen them struggling against the intensity of the feelings that are developing between them, alternately very cold and very hot, dancing back and forth trying to escape the heat of their relationship yet unable to resist its power. Almasy alternately intensely pursues K (stalking her at the market, “predatory” stare during the dance, etc.) and rejects her, to the point of being openly rude (in the car, re her drawings in his book). He goes out of his way to tell her husband he shouldn’t leave her alone in the desert, as if trying to warn him of what will occur. (And in that scene we watch a receding Geoffrey walk away from Katherine toward his plane while Almasy looks back at her, one husband moving out as another one moves in, changing of the guard a la Gyges story.) He journals about the meaning of betrayal, he looks openly frustrated and upset when he realizes they will be alone together in the desert overnight, he rejects her drawings. He is fighting against himself, and losing.

When they arrive back at the hotel after the night in the desert she invites him to come in and he refuses, pointedly calling her “Mrs. Clifton,” reminding her that she is another man’s wife. They both understand what is going on here: he is not going to make it easy for her, not going to come to her room so things can “just happen”. She will have to be the one to break her vows, to make a conscious and deliberate choice, he will not initiate the act of adultery. Katherine understands this, and she does come, but she is angry at him and at herself for what she is choosing to do, and angry that he has forced her to acknowledge that she wants this as much as he does. This is why she slaps him. The slap and desperate, hungry sex are the expression of the violent emotion, passion and tension that has built up all along.

Even though she knew what was going to happen, she wanted do as as a married women would and at least fake like she had some honor...Remember when they first got back she said come in with me and he had to remind her that she was married woman, as she had not even though how it would look with him going into her hotel room. So when she returned to his place she was simply going through the motions of trying to hold on to the slightest bit of dignity she could, if he had backed off she would have acted As she was supposed to, but she knew he would continue as her being married he could care less about.