Tell her its the only academics that matter.

Problem Solved.
Did I mention she was a teenager? She wants to go to another school that is just as good but way more diverse. She shouldn't have to put up with racist BS because of academics.
How minority kids are treated in schools by the majority has a lot to do with where the school is located. In areas where a minority is considered to be a threat, be them Blacks, White, Latinos, or Orientals, parents will caution their children and often impart to them their own prejudices. The results are often a pretty bad experience for the minority kids. If I were in such a situation, I would try to move to an area with a good mix of minorities and above average family income where kids are likely to be judged on own merits not their skin color or ethnicity.
I have grandkids in northern Florida and Seattle. There is a huge difference in how minority kids are treated in school. My granddaughter in Seattle is a teenager and dates white, black, and oriental kids. When she has a sleep over, there's a real mix races, religions, and ethnicity. That is certainly not the case with my grandson in Florida.