No one, well at least me, is asking for realism. I'm, and other are, asking for believability. Fucking Leon over a kiss after everything that was said in bed between Clara and Alan makes no sense. As I said, it would make more sense she maybe broke down and but caught herself and stopped it before the fucking started.
Who goes, fuck me Leon, cum in me. Then next time, don't put it in I don't want to fuck you because I love Alan. What, next time it will be, we can't have sex but let me give you a handy...
It's not believable, everything else in the story up to this one point is acceptable. She would have confronted Alan and Anna about the kiss based on the strength of her character set up by the Dev. The Dev literally says Clara is a intelligent, strong willed, and independent woman, who is also an elite agent.
There is no way she would not open that door and ask Alan what was going on, or go back to her room and call Alan and confront him. Then it would be separate rooms for Alan and Anna, or Alan would start living with her under the guise she wants him closer for work.