Your woman has amazing hair -- congratulations! I'm glad to hear you get to enjoy it on your chest and face while she's blowing you, and while you're doggying her.
But if you really want a hairjob, which I assume you do, there's ways to get it without spilling the beans about how attracted you are to her hair.
Do you tell her how soft her hair is? How good it feels against your skin? If you casually told her how silky her hair feels on your chest, maybe she'd figure out on her own that it would also feel amazing around your cock. Or if she's on top, if you could get her to let her hair fall around your face, you could tell her how great it feels.
Doing something fun with her hair in a playful way that makes her laugh is always going to get you farther than confessing a fetish.
Best of luck to you!