[clarification needed] Tully grew up in Delray Beach, Florida and won state titles in running while attending Pope John Paul II High School briefly attended Wake Forest University[1] but, dissatisfied with her running development, transferred to her parents' alma mater.

[2][3] Running for the Villanova Wildcats under coach Gina Procaccio, in her freshman year Tully placed sixth in the 1500 meters at the Atlantic Coast Conference championships.

In her first appearance on the major international track circuit, she set a 3000 m best of 8:55.48 minutes to place tenth at the adidas Grand Prix in New York.

[8] She ran her first 5000 meters at the Payton Jordan Invitational in May and surprised by taking third in a time of 15:05.58 minutes – this met the qualifying standard for the national team and was over 25 seconds faster than she anticipated before the race.

In her second outing over the distance she won the national title at the 2015 USA Outdoor Track and Field Championships, beating much favoured opposition.