Born in Athens, Papachristou won the bronze medal at the 2008 World Junior Championships. She competed in the 2009 European Indoor Championships and went through the qualification round with a jump of 14.47 metres. However, in the final, she was injured and failed to register a valid jump. After taking the bronze medal at the 2009 Mediterranean Games, she competed at the 2009 World Championships without reaching the final round. She won the gold medal at the 2009 European U23 Championships that season. During the indoor season of 2011, she competed in the qualifying rounds of the 2011 European Athletics Indoor Championships without reaching the final. She achieved a personal best of 14.72 metres in June 2011 in Chania – a mark which ranks her third among Greek female triple jumpers, after Hrysopiyi Devetzi and Paraskevi Tsiamita. This jump was also the second best ever achieved by a European under-23 athlete after Anna Pyatykh's record of 14.79 m. She successfully defended her gold medal at the 2011 European U23 Championships in Ostrava, Czech Republic.