As Ira Levin's son Nicholas discusses in a new afterword to Levin's later Son of Rosemary, Terry appears to have been intended as an important foil to Rosemary. So central was Terry in fact, she's the culminating image in Rosemary's protracted "dream" sequence. (That dream image – of Terry sitting inside the Pope's tannis-charm ring – was purportedly omitted from the '68 movie due only to an inability to realize it on film.)
Apartment 7A takes its name from the Castevet's place of residence, and stars Julia Garner as Terry, and Dianne Wiest as Minnie Castevet.