A young woman, Lauren, who used to be a member of this forum wrote me a personal message in which she said "I like the idea of pulling another woman's hair, if I was to be honest. A woman takes great pride in her hair, so to attack that which she prizes above all else is the main focus of most female fights. I love the power it gives me if I manage to grab two tight fistfulls [of hair] and drag the other bitch to the floor."
Women dress as much for each other as they do for men. It's also the same with their hair -- they show it off as much to try and out-shine one another as to attract men. In that sense, it's both a source of pride and power. And, the longer a woman wears her hair, the more its an obvious source of pride to her because of the extra time, energy, and money she has to devote to its care.
When women attack each other's hair, particularly if its long, it a very personal attack because they're going after the very thing which helps to define their outward persona. How they present themselves to the world is a statement about who they are and their hair is a big part of that presentation of self.
Seeing two girls/women pulling hair is sexy because you're watching them go after each other in the most primal sort of way -- attacking their opponent's silken tresses to not only cause pain, but to mess-up and destroy their rival's hairdo, a powerful source of defining their femaleness and sexuality. Look at all the ads for women's hair products -- they are pitching products to not only make them more attractive, but to make them more sexy. Which is why, in most female fights, their hair is the first thing the two combatants go for and why, for me, its so sexy to watch. Hairpulling is what makes a catfight, a catfight.