first of all, congratulations for finding a girl! and huge respect for telling her! i would not dare that unless i would be 100% sure that she still likes me afterwards. showing her pictures of the curezone gallery is another brave step. there are some pretty ugly pictures on here. must be a really cool girl if she doesn't care.
and no, this is definitely not contagious. before i broke up with my ex-girlfriend almost 2 years ago, i kissed her for several months and she never got it. and i had another girl in the meantime, she didn't catch it either (and didn't notice it btw). some other guys & girls on here have boy-/girlfriends and none of them caught it.
this is something internal, i reckon it's genetic. that's what my dermatologist said to me and i think it makes the most sense. so tell your girl that there's no chance of her catching it.