I would leave your wife's fantasies and thoughts alone. Everyone has them. It's not like she actually is contacting the guy and going to see him. Many people has role models and sexual "heartthrobs".

I would ask ask her for the poem and then ask her what you would need to do to make her feel like that ("new") and/or give her kisses on her neck, etc. Focus on what you know she likes (instead of what you dislike?) and try to give it to her. Pulling away and being upset with her will not make you all closer?

There's a nice little tale I like about a Roman boy learning weapons training from an old soldier and complaining that his sword was too short and the weapons master replied to him, "Then step closer to the foe!"