By the time of her flight she will have hopefully recovered. She can then get a note from a health care provider stating that she has recently recovered from covid. This statement plus her positive covid test from what will have been within 90 days prior to the flight should be sufficient. Technically people can test positive for up to 3 months after infection so this updated provision allows people who have recently been infected, but have recovered, to travel
https://www.cdc.gov/coronavirus/2019-ncov/travelers/testing-international-air-travelers.html