According to TVLine, Foster’s presence places a strain on Kara’s relationship with Cat as she and Foster develop an unexpected relationship.
Benoist, 27, announced the news by posting an Instagram photo Wednesday of Jenner on set and captioning it: “Coming to National City.”
Jenner and Benoist married this past spring after reportedly getting engaged in July 2013.
Supergirl airs Mondays (8 p.m. ET) on CBS, and Jenner’s upcoming episodes are set to air in 2016.