Hornbrook is very involved in helping women realize their potential in STEM and enter STEM fields. She has served as a mentor for the PROGRESS campaign (Promoting Geoscience Research Education and Success) which pairs women with an interest in geosciences with a mentor in a geoscience field. In 2016, Hornbrook also visited Mackintosh Academy in Boulder, Colorado to run a workshop for girls in science.
Hornbrook has also served as a mentor for the Significant Opportunities in Atmospheric Research and Science (SOARS) program. The program works to help students from underrepresented groups have an opportunity to conduct research related to atmospheric sciences.