Complex sentence: She has continued to be involved with Modern Pentathlon when London became the host city for the 2012 Summer Olympics, becoming the Fencing manager for the Pentathlon event at the Games.
Split into simpler sentences: She has continued to be involved with Modern Pentathlon. When London became the host city for the 2012 Summer Olympics, Kate was chosen to be the Director of Fence for the Modern Pentathlon event at the Games.