Kim Yo Jong, believed to be in her late 20s, attended the third inter-Korea summit in Pyongyang at the Korean Workers' Party headquarters from 3:45 to 5:45 p.m., South Korean news service News 1 reported Tuesday.
Kim Yo Jong appeared to be on equal footing with senior officials like Kim Yong Chol, the vice chairman of the party's central committee, and Kim Jong Un's envoy to the White House earlier this year.
Kim Yo Jong was seen at the meeting occupying a seat that was equal to top South Korean envoys at the table, including Suh Hoon, South Korea's chief of the National Intelligence Service, and Chung Eui-yong, South Korean President Moon Jae-in's national security adviser.
Earlier in the day, she appeared to be in charge of the welcome ceremony at Pyongyang's Sunan Airport, where Moon received his first welcome then was guided to Paek Hwa Won Guesthouse.
Kim Yo Jong played a key role as her brother's messenger ahead of the 2018 Pyeongchang Winter Olympics, meeting with Moon then relaying Moon's missives to Kim Jong Un.
She has become more prominent in North Korea's foreign affairs, but is less visible in domestic North Korea meetings, according to News 1.
The Korea Times reported Tuesday Suh's presence at the meetings are a sign the South Korean spy chief has played a pivotal role in building ties between North and South.
Analysts who spoke to the paper have said the "Suh Hoon-Kim Yong Chol" line has become critical to maintaining behind-the-scenes contact between the governments.
Moon concludes his trip to Pyongyang on Thursday.