Dear vinlee:
Since it is not possible for your parents to talk to her parents and her parents will not allow her to see you, and she is a minor and living with her parents, dependent on them, unfortunately, there is nothing you can do, nothing that will be successful.
If you think that the reason her parents rejected you is because you are not “that good looking” – other than dressing better and keeping yourself well groomed, there is nothing you can do about that either.
If you believe that you are not good looking, then, there is something you can do about that- eat better, exercise, keep yourself well groomed and dressed neatly.
And if you believe that you are not clever enough, there is something you can do about that too: learn from your life experiences, get curious.
anita