Emma, who lived in Oak Hill, unexpectedly died on Wednesday. The cause of death has not been released.
She had been a member of chorus groups and the South Lakes softball team, classmates said. She also held a part-time job at Life Time Athletic in Reston.
The Class of 2015 encouraged one another to wear green to school on Friday in memory of Emma. The students also signed a giant banner in Emma’s honor.
The class is planning a candlelight vigil Friday night near the Monroe Manor neighborhood where Emma lived.
Students from South Lakes and neighboring schools took to Twitter with messages with the hashtag #RIPEmma.
South Lakes received flowers and a note of support from Langley High School students. Two Langley students committed suicide the same week during the 2013-14 school year.