I think she's "Ellen Barkin", because as per IMDB http://imdb.com/name/nm0000289/ she played the role of "Princess Henrietta" in the "The Princess Who Had Never Laughed"
It's the governess getting tickled. She's the lady from "Eating Raoul," and the evil nurse in "Night of the Comet." She's been in tons of stuff, including Rock and Roll High School, where she plays the principal.
I remember that movie. . . Everyone was all stuck up and unhappy until the Princess started laughing then people were able to relax. The governess gets tickled in the ending narration sequence. The man doing the tickling is the Princess's tutor.
i remember WATCHING the movie as a child, but don't remember much from it since it was so long ago, but i remember wondering and asking my parents or teacher or whoever showed it to me "well if they can't get her to laugh with jokes and tricks, why don't they just tickle her???"
Mary Woronov also played the warden in Prison A Go-Go, in which Rhonda Shear got her foot tickled. So maybe there's a new game here: now we have to find a movie Rhonda appeared in in which someone else got tickled, and so on and on.....