Samantha Futerman as Lydia Hye ( Season 4 ) , a friendless , overachieving student at Westhill who Cathy hires to be Adam 's Chemistry tutor .
Tutor is failing the class .
Samantha Futerman as Lydia Hye ( Season 4 ) , a friendless , overachieving student at Westhill who Cathy hires to be Adam 's Chemistry tutor , because he is failing the class .