After struggling with injuries much of her college career at the University of Notre Dame, Sullivan rediscovered her potential as a post-collegiate marathoner. While balancing her training with a career as a middle school math teacher and volunteer coach at George Mason University, she has continuously improved year over year, finishing the 2020 U.S. Olympic Marathon Trials and qualifying for the 2024 trials by running 2:24:27 as the top American at the London Marathon in 2023.