@skieurope … I’m sure that the OP is not the only person ever to learn about their heritage in a way that motivates them to reconsider ethnicity with respect to college admission.
I am asking not just because your posting suggests that AOs will suspect fraud that does not exist, but because I have no first-hand information… Do you have any first-hand information or knowledge of an AO suspecting fraud? Or is this what your imagination suggests.
I strongly feel that if the raised eyebrow of the AO exists in your imagination, and not in your experience, that the OP should contact the admissions office at any potential school, explain the situation, and ask for advice. Otherwise, the OP might miss an opportunity that is genuine, ethical and valuable.
Also, the definition of underrepresented minority that you posted is one of the most narrow definitions that I have read so far. The OP should be aware of this, and use the definition of ‘Hispanic’ that is used for the context of the application that asks the question … usually much more broad.
P.S. I hope the OP checks ‘Hispanic’ for the PSAT… the NHRP designation is correctly given to the OP if her scores meet the criteria!