Girls this nice don't exist
I myself am the same type of "child in a man's body". I'm 29 and most girls my age tell me it's not working out because I'm too immature or that I'm like a "man-child". I guess the girl in the movie was nice to him because she felt sorry for him. I think she liked him as a hug buddy, but ultimately women are drawn to alpha males as mating partners. And I don't think it's uncommon for girls to have like platonic sleepovers with a male friend.
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"Knightley is a poor man's Portman." -monkeypunks