I think we can all agree that it's hard to distinguish "reality" from "fiction" in Lolita. As many people have pointed out, Lo herself seems to have initiated some of the sexual interaction between her and Humbert; however, as others validly claim, Humbert isn't exactly unbiased. He's trying to manipulate the reader because, even if he weren't trying to justify his actions, that's just who he is. We see his penchant for manipulation throughout the novel as he talks about toying with his psychiatrists and how he loves games and stratagems. We are his pawns.
Second, even if Humbert were doing everything within his power to remain as neutral as possible in his account, his character is too mentally unstable to make sound judgments about the world. Is it just me, or did it seem that everywhere he and Lo went there were just more pedophiles? Cue was almost jailed because he "liked little girls" and Gaston Godin was "caressed by the young--oh, having a grand time and fooling everybody." Then there are the seemingly countless (I certainly can't remember how many) number of men who eye Lo with a "lecherous grin."
This rampant pedophilia disturbed me, so I looked up some stats. Convicted child molesters (some of which I'm sure are women) make up roughly .08% of the U.S. population. If we buffer that number with a generous .02% for uncaught/acquitted child molesters, that's still only 1% of the population. (Of course this says nothing about people who have attraction to children but don't ever act upon it, but I'm sure that's still less common than the way Humbert depicts it.) Nabokov probably didn't look up the stats, but still, Humbert is delusional and paranoid. Lolita might have been a pretty little girl, but I don't think she was a deliberate temptress. Humbert found her attractive, perhaps saw her as a seductress because he was seduced by her, and then impressed upon other people his own feelings about her.
Maybe. I'm still making my mind up about Lo, but this is one of the possibilities.