At the end of season 2. Her character is killed by the terrorist Ari Haswari.
Kate Todd is played by Sasha Alexander, who left the season for personal reasons. Her character, Kate, is an ex-Secret Service agent who was invited to join NCIS by Agent Gibbs after she disobeyed a superior. She did not leave for personal reasons, she died, shot by Ari, Ziva's half-brother.
Washington DC
No. Kate was just played by one person - Sasha Alexander
Todd
Yes, Ziva left NCIS.
Kate Todd is played by Sasha Alexander, who left the season for personal reasons. Her character, Kate, is an ex-Secret Service agent who was invited to join NCIS by Agent Gibbs after she disobeyed a superior. She did not leave for personal reasons, she died, shot by Ari, Ziva's half-brother.
No
No. She died.
Washington DC
No. Kate was just played by one person - Sasha Alexander
Todd
Yes, Ziva left NCIS.
Gibbs and Gearld
We never found out on the show.
Wendy Makkena
She was awarded the Presidential Medal of Freedom posthumously
The episode mentioned above is Bete Noir, which was aired in Season One of NCIS.