It's still bizarre desperation, though. There are plenty of adolescent girls who are ostracized and rejected, who fail to grasp the basic principles of socializing, who have surreal sets of obscure interests, who have hopelessly tangled interior monologues, who wander alone in the intricacies of their fantasies, and who are weirder than they are hot (at least for the time being). The isolation they feel may be more isolation from community and romance than isolation from sex -- hence the preference for shipping over slash -- but I doubt that makes their desperation much less consuming.
This pretty much nails it. Speaking as a former awkward adolescent girl (I'm still awkward, but at 23 you can't really call yourself "adolescent" anymore), I can say with some confidence that what you're really fantasizing about at that point is belonging: being in love (possibly with Maximum Cuddles as an option, but these are less important than the True Love) and loved, ideally by one Significant Other and as many adoring friends as possible. This obviously lends itself to shipper fanfiction -- but, I think, particularly shipping of awkward couples, people who really shouldn't get together (because they have nothing in common, or because cruel society keeps them apart, or perhaps because one of them is Harry Potter and the other is Legolas), because what good is it for twisted desperate wish fulfillment writing about the love lives of serene, happy, confident people? You know you're not a serene, happy, confident person. But you might be Harry Potter, and Legolas
just might show up.Possibly the best example of this I ever read was by a middle-school friend of mine, quite possibly the most awkward adolescent girl I've ever met, who wrote fanfiction about the Disney version of Hercules. The first such fanfic (in what turned out to be a series of 3, plus bonus installments) was about a girl who was the secret, abandoned daughter of Aeneas and the muse Erato, living as a beggar despite her incredible beauty and prodigious musical talent. She meets Hercules, they fall in love, she turns out to have psychic powers, Hercules has a crisis because he has a pre-existing love interest, it turns out the beggar girl is the love interest's childhood best friend, and so on... until, inevitably, there is a conflict with an Evil Guy in which the beggar girl dies tragically so that Hercules can be with his love interest, and everyone mourns. Seriously, everyone. All the Olympian gods and stuff. It is such an archetypal Work Of Fanfiction By An Awkward Adolescent Girl that I almost can't believe I really did encounter it in the wild, from an author who apparently had no awareness of fandom as a phenomenon. (Later on her work got more self-aware, right down to inserting characters "inspired by" her friends as bizarre, frequently antagonistic supporting cast, which is less archetypal but also symptomatic of adolescent desperation in strange ways. Honestly, she as a person was a psychology thesis waiting to happen...)