Swift, 22, posed arm-in-arm with Ethel, 83, at the Friday premier of "Ethel," a documentary about the venerable social activist.
The Los Angeles Times said Saturday that while it wasn't clear what brought young Taylor to Utah, she told Vogue in a recent interview that she was an admirer of Ethel's high-profile marriage to Robert Kennedy in the 1960s.
"You look back at the pictures of her and Bobby, they always look like they are having the most fun out of everybody," Swift told the magazine.
The Times said Kennedy was accompanied to Sundance with family members including daughter Rory, who directed "Ethel."
The Kennedy film was one of the opening-day presentations at Sundance. EW.com said the influential festival appeared fairly dour based on the many documentaries making their premiers; however a closer look at the roster reveals some upbeat comedies and dramas that are actually "more touching than harrowing."