Well, if you really love this girl tell her that and then tell her about your hair fetish. If she you she will grow her hair out. I told my wife when we were getting serious. I got up the courage to ask to wash her hair over the kitchen sink, she just said, yea, I was going to wash it anyway. Her hair was about to her bra-strap thick straight and brunette . I told her about my love for long hair and my fetish for washing it and brushing it, and that I wanted her to grow it to her butt crack. She wasn't crazy about letting it grow that long but she did. We have been married for 41 years now and her hair has been varying lengths, from waist to shoulder length. But she always lets me wash her hair in a forward manner over the kitchen sink, dry it and brush it, which leads to hot sex. In fact I am washing her hair tonight.