In her first major race of the 2104 indoor season Mary set a new World Junior Indoor 1000m Record with a time of 2:39.25 at Boston University. One week later at the same track she just missed the World Junior Indoor mile record but 0.01 secs recording a time of 4:24.11 which is the second fastest in history and an American Junior Indoor Record. She followed these wins with two more major wins in the Boston Indoor Games and Millrose Games. In Boston she further improved her World Junior Record to 2:35.80 before winning the Millrose Games Wannamaker mile in 4:27.73. She closed her indoor season with a very impressive win in the USATF 1500m Championships in Albuquerque. This performance qualified her for the IAAF World Indoor T&F Championships in Poland but she took the wise decision not to take part due to a soreness in her leg.