Billings portrays a transgender character who's expected to be influential in the lives of the Conner family and figures prominently in tonight's episode.
Gilbert and Perry have been married since 2014.
Sara Gilbert's 12-year-old TV son Mark comes out as gay in an episode that highlights the importance of love and support for LGBTQ kids.
Barr said that she and Gilbert no longer speak.
Gilbert recently announced she was leaving The Talk, which she helped to create, to balance work and family.
The out actress and producer explained why she's leaving after nine seasons.
The cohost of The Talk spoke for the first time about the series' cancellation following Barr's racist tweet, and said the show has always been about "diversity, love, and inclusion."