While at Mt. Pleasant, she won the both the 100 meters and 200 meters at the CIF California State Meet both her 2006 junior and 2007 senior years. She was also part of the 2007 CIF State Championship team from Mt.Pleasant High School.
On June 23, 2012 Tarmoh finished in a tie with Allyson Felix for third place in the 100m finals at the US Track and Field Olympic Trials. Tarmoh had initially been declared the third-place finisher immediately after the race but was dropped into a tie with Felix after officials reviewed the photo finish of their finish. The top three places qualified for the 2012 USA Olympic team for the 2012 Summer Olympics; however, USATF had no tiebreaker procedures in place at the time in the event of a tie for the final spot. After discussion, USATF officials decided that a runoff between the two sprinters would take place in the event that neither ceded her spot to the other. Tarmoh initially agreed to the runoff, but later pulled out, ceding the spot to Felix. The event generated substantial criticism toward USATF officials for having insufficient procedures in place for breaking ties, as well as for forcing the runners to decide whether to participate in the eventual runoff.
Tarmoh traveled to London as a reserve on the US team. She ran the second leg of the women's 4 × 100 metres relay in the qualifying round. Although she did not compete in the finals, she received a gold medal as the USA set a world record in winning the finals.