But the enchanter is written a good 10 years before that, and is very much a diet Lolita, with all these similarities there already.
Considering the amount of times he has written about young girls, I don't think he needed all that much inspiration other than his own mind. He manages to get it into even books that has very little to do with the subject, like Transparent Things as well.
Being nabokov he of course rejects any idea of him projecting himself into his characters. But you gotta start wondering, when it's such a common theme through his books.