Fair enough! And glad to have this sorted out.
I think having heard the full thought process the only thing I can say is its somewhat limiting to presume that the character would use and relate to the f slur in this way, like it precludes any other relationship with the word or any other expression of transness. Which as a trans woman, to me is kinda sad. But like, it seems like you're specifically angling for this expression of transness so I can't ultimately fault it. My original assumption that the f slur was out of place here wasn't accurate, so my bad ^^