* The 1994 live-action movie "The Flintstones" used a combination of animatronics and voice acting for the role of Pebbles. The voice of Pebbles was provided by Holly Hunter.
* The 2000 direct-to-video sequel "The Flintstones in Viva Rock Vegas" also used animatronics and voice acting. Pebbles' voice was provided by Kristen Dunst.
So, while there's no real actress who played Pebbles in a movie, those are the two actresses who provided the voice for the character in the live-action films.