Great question!
My beautiful wife has known since before we were married in the 1980s that I have a fetish for her hair. It's about brastrap length now, and I'm still getting regular hairjobs.
However, we never really talk about whether I'm attracted to other women's hair, and if she has any clue about my online activity, she's never mentioned it.
I had a friend in high school who I told about my hair fetish - he liked long hair, too. But we had a falling out years ago. Nobody else IRL knows.
For those of us who are lucky enough to have a woman with hair - long or short - in your life, you don't have to name your desire for her hair. Don't tell her you have a fetish. Just tell her you think she has great hair. Tell her how good and silky it feels against your face or your stomach. If she still doesn't get the hint, be more direct. But let it come from a place of love and desire for her.