By Tom Gliatto
Updated March 08, 1999 12:00 PM

Diane Keaton, Juliette Lewis

Just as Pretty Woman was a feel-good romantic comedy about a prostitute, so The Other Sister is a feel-good romantic comedy about a young woman (Lewis) who is mentally disabled. And just as director Garry Marshall had to do mighty fancy footwork in Pretty Woman to make his sidewalk hostess heroine seem like the lovable Ivory-girl next door, so here he gives us the rosiest view possible of everyday life for a person whose brain hums slower than those of most folk.

There are amusing and even inspirational moments in Lewis’s battle to find a life and love apart from that of her overprotective, disapproving mom (Keaton), but Sister is as soft and gooey as a marshmallow. Lewis and Keaton both overplay their roles, but Giovanni Ribisi (Frank Jr. on TV’s Friends), playing Lewis’s even slower beau, captures exactly a guy doing his best despite sizable limitations. (PG-13)

Bottom Line: So sweet it hurts