Is "Lolita" really an innocent girl? If not, what are the circumstances that put her into the bad situation?
This answer can go either way, depending on how you want to support it. In the book, How to Read Like a Professor, Thomas Foster notes that, "every story about the loss of innocence is really about someone's private reenactment of the fall from grace, since we experience it...individually and subjectively" (49). The "fall from grace" that Foster refers to is a moment when, for the first time, a character experiences a tragic dichotomy between his expectations and reality. In other words, the character expects something but reality falls dramatically short of that expectation. Think of any story where an adolescent boy asks out a girl but realizes, either on his own or by another person, that he will not be able to go out with her. That is a moment of lost innocence.
As an isolated act, Lolita losing her virginity is not necessarily a lose of innocence. Instead, it would depend on how much insight the reader had about the character at the moment when her virginity was lost. Lolita told Humbert that she lost her virginity with another girl at Camp Q. However, the reader does not know what her sexual expectations were before that moment.
Others might say that, before any intimate encounters at Camp Q or with Humbert, Lolita was not innocent because of her general behavior; her manners were course and uncultivated. Moreover, she seemed to speak with a sardonic wit of an older curmudgeon. Nonetheless, none of this matches up with the description that Foster gives us for lost innocence.
In my opinion, she did not lose her innocence until Humbert was sexually abusing her. It was during only these times, when she would helplessly express or literally say "no," or when she conveyed a sense of doom about the approaching night and the sexual acts that Humbert was going to commit, that she experienced a true difference between her expectations and reality. Lolita eventually becomes indifferent to Humbert's abuse, conveying that the innocence is lost and a new reality is accepted.
"Lolita" is a novel so skillfully and artistically written that the reader almost accepts the memoir as a "love story." Told from the point of view of Humbert Humbert, the reader is unsure what actually transpires. Nevertheless, one does know that Humbert marries Charlotte Haze in order to be close to the twelve-year-old daughter.
In Part II Charlotte/Lolita is taken to a motel after her mother's death, Humbert climbs into bed with her after she falls asleep. He narrates, "I am going to tell you something very strange: It was she who seduced me." After waking, as Lolita kisses Humbert, he notices that she has knowledge of kissing, he whispers--she is a "nymphet." He finds no "traces of modesty in this beautiful...girl." Humbert claims no interest in the "elements of animality";his is a greater endeavor: "to fix once for all the perilous magic of nymphets."
Despite her lack of naivete, Lolita does not seem to be truly experienced. For, after a couple of weeks, the girl seems listless and unhappy, an indication that she probably was not truly interested in a relationship, instead, she may have felt the need to show her sophistication to the man whom her mother had seduced--a type of feminine jealousy/competiveness,perhaps.