An animated movie with a dark skinned, white haired girl who is 1000+ years old?

I remember never getting to finish this movie when I was younger.
What I remember most vividly was a girl, she was older than she
looked. I think she was over 1000 years old. She had dark skin, her
hair was white and I believe she had blue eyes and blue markings on
one of her cheeks.
There was also this guy, I think he was one of the important
characters. He had kind of a bowl cut, his hair was brown, he had
these big round Harry Potter-like glasses, and was scrawny and nerdy
looking. I think he liked the white haired girl.

I also remember a part, where I think the girl tells him she is a part
of this thing(member of group, organization, etc.) just because she
was there. The the scrawny nerdy guy does the math and comes up with
the answer she is over a 1000 years old. She doesn't know what to
think of his surprised reaction, he just end sup telling her she looks
good(considering how old she is).