Kate Fitz, where’d you get those notions? The check box is optional. Guidelines come from the Census/Dept of Labor, which also allows self-reporting. There are some fine points, for some of the check boxes, but no one expects all Asian-Americans to have an Asian last name or participate in a culture club. No one will examine OP to see if she “looks” 1/4 Chinese.
She has always identified as Caucasian, her own choice, her own matter of simplifying. She can now choose for the college app.