She, along with fellow clone Alison Hendrix first meet Sarah Manning whilst the latter is under the guise of Beth Childs.
student and a clone of American origin on Orphan Black.
In "Natural Selection", after Sarah Manning assumed Beth's identity, Cosima still kept calling Beth's phone.
In "Effects of External Conditions", Cosima examines Helena's knife and tries to explain her motives for killing in a video chat with Sarah and Felix.
Later, Cosima calls Sarah and tells her that Helena is connected to Maggie Chen, the woman that Beth shot. Sarah tells Cosima that Helena was at the police station and wants to meet her.
Cosima tells Sarah that she needs to keep being Beth to learn more about who's killing them.
Cosima tells her to hinder the police's investigation into Katja's identity.
Cosima tells Sarah to get rid of the body and get Katja's hair and blood samples. She tells Alison, who doesn't believe that Beth committed suicide, that Beth was "losing it clinically".
Later, Cosima calls Bet(who is actually Sarah) and tells her to get Katja's briefcase. Cosima tells Sarah that she wanted to explain the whole clone thing more softly after Alison blurts it out.Sarah meets Cosima at a local bar on the day she is set to return to Minneapolis for her studies and gives her the briefcase.Cosima tells Sarah that six months ago, Katja contacted Beth and then Beth found Cosima and Alison.Cosima says that if it was her experiment she'd put an observer close to the subject. She asks Scott to help her but doesn't tell him what it's for.She notices an upset Delphine who leaves behind her report card.Sarah, as Beth, tells Cosima that the German is dead and they both panic. Cosima introduces herself to Sarah at Alison's house.