Can you treat the fantasy like an intrusive thought and use DBT type skills?? I suffer from body dysmorphia and an eating disorder and sometimes I will have intrusive thoughts where I comparing my body to my Ts body ( female, close in age, athletic). These thoughts are unwanted, extremely disruptive to my therapy and connection, and generally not helped at all by talking about them.
With these thoughts often comes the feeling/fear that my T is secretly critical/ashamed of me.
I use my DBT skills. I tell myself these thoughts are not useful and focus on something else on in the room ( carpet pattern. Something like that) til I get it out of my head....