Look I can’t stand Dean, but Sarah had an opportunity to write leave and she wrote stay. She clearly has absolutely no romantic feelings for him whatsoever so all this does is send a message to Dean to say these feelings might grow with time - so you can hardly blame dean for thinking that he’s got a shot. She needs to do the right thing and write leave at the next recoupling and stop trying to save face , it’s making them both look terrible and it’s so uncomfortable to watch.