I've had friends with nice hair and I would have lot to do many dirty things with it. But I would say first that if you want to keep the person as a friend you better not tell her that you dream of cumming on her hair. And if your goal is to be more than just friends, you could compliment her hair often to slowly make her understand you are into hair. Because just telling "i have a hair fetish" could be weird (even if it's not) and the slow method is the best I suppose.

And anyway if you ever manage to realize your dreams with her hair, show us the results hehehe

And good luck