To me, if you do something romantic with another person or intended to strengthen a romantic connection, then you are cheating on your waifu. Obviously, if you have sex with or kiss someone else then that's cheating too. Outside of things like that, I can't really consider anything else "cheating". In the end, I think you should be considerate of how she would feel about certain things. If you fap to porn that's not of her and neglect her sexually, then she might be unhappy about that, but I wouldn't say it's cheating.