Would you give your b/f or g/f another chance if you found out that she/he cheated on you? To be more specific, nothing really happened physically. She/he just started developing feelings for someone else. Also, the fact that you've had suspicions before about him/her cheating, makes the case stronger. Now, in my opinion, that's enough to leave him/her. Cheating is cheating, there is no in between. If she/he was "looking" for someone else, why not just end it right then and there right? So, basically, would you end a relationship based on the fact that your significant other developed feelings for someone else? Which he/she says is now gone.