I can imagine the guy who writes the codes, when seeing the codes written so wonderfully by someone else, uttering involuntarily “Wow!”. The logic behind this scene is that he has “seen” the codes, but he never wrote that way. He can’t say “the most beautiful code I never saw”. Besides, goes back to my first responding post, it also has a function in echoing the second line.
“It's the most beautiful place I never went” and the example you gave “She is the most beautiful girl I never met”, fall into the same fault. You have to “see” it to make any conclusion.
Change your sentence to “She is the most beautiful girl I never dreamt of/dated/kissed”, it is logically sound, because obviously you have “seen” her and knows how beautiful she is, but never dreamt of her/dated/kissed whatever. But this pattern is still an awkward way to express an intense feeling, which is one more reason to avoid it, unless you have a really good reason to take the risk.