Golightly has landed a recurring role in the show, Deadline reports.
Ringer stars Sarah Michelle Gellar as a woman on the run who assumes the identity of her twin sister Siobhan, only to realise that Siobhan's life is not as perfect as it seems.
Golightly has now signed up to play a tough student at the school attended by Siobhan's stepdaughter Juliet (Zoey Deutch).
Golightly previously appeared as Hayley in The Troop and played Thea in Heartland. Her other credits include guest roles in Big Time Rush and True Jackson, VP.
Jason Dohring also recently signed up for a role in Ringer and will play a teacher at Juliet's school.
Other stars who will appear in the drama, which premieres on The CW on September 13, include Billy Miller, Michelle Stafford, Justin Bruening, Ioan Gruffudd, Jaime Murray, Kristoffer Polaha and Nestor Carbonell. The show will air on Sky Living in the UK.
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Watch a trailer for Ringer below: