[8] At the turn of the century, she received a UPenn University Research Foundation Award to fund her projects Identifying and Reaching Populations at Risk: The Paradox of Cancer Control[9] and Housestaff Depression and Career Choices.

[19] In 2017, Armstrong received UPenn's Pioneer Award for her "achievements and rise to some of the highest health care posts in government and academic medicine.

[24] On March 1, 2022, Armstrong became the chief executive officer of Columbia University Irving Medical Center and Dean of the Faculties of Health Sciences and the Vagelos College of Physicians and Surgeons.

[25] She also is Executive Vice President for Health and Biomedical Sciences for Columbia University and the Harold and Margaret Hatch Professor in the Faculty of Medicine.

[26][27] In September 2024, Armstrong apologized to pro-Palestinian students and others "hurt" by mass arrests conducted by the NYPD at Columbia's behest earlier in the year.

Her work has focused on cancer risk and prevention in Black and Latin patients,[32] examined racial inequities in genetic testing and neonatal care, and analyzed the roles that segregation, discrimination, and distrust play in the health of marginalized populations.

[33] Her most recent research studied disparities in rural areas and include partnerships with Lakota tribal communities and organizations in western South Dakota.

[34] While attending Johns Hopkins University in the Osler residency program, she met her future husband Tom Randall, a gynecologic oncologist, and married him upon graduation.