Lappi-Seppälä played in the Finnish women's premier division 1990–2009 for HJK, FC United, FC Espoo, Åland United and PuiU. During the winter periods she played in Belgium, the United States and Italy. Lappi-Seppälä earned 21 caps for the Finland women's national team.[6]
In 2019–2021 Lappi-Seppälä was the head coach of FC Honka in the Finnish women's top division Kansallinen Liiga.[6] In February 2023, she was appointed the manager of the Saudi Arabia women's national team.[7][8][9][10][11]