Can someone help me find an old anime TV series please?

I think it was aired in somewhere around 2000–2008 and it had a young adult female with what I recall as being light blue long hair and she was on the run. A boy of the same age accompanied her and helped her. She was some kind of scientific experiment of alien. It was set in the future. I believe the boy and girl (main character) also had a love interest. Sorry I don’t remember much about the show. Any suggestions would be more than appreciated!