The movie is I think called Carolyn about a woman who comes back home clamming to be Carolyn to one clam and inheritance, two the help two children one who is artistic and one who needs to gain his independence

Caroline? (1990 TV movie)
Starring Stephanie Zimbalist, Pamela Reed, George Grizzard
IMDb synopsis:
A mysterious woman claiming to be the deceased daughter of a rich man tries to solve the problems of his untrusting son and supposedly mentally handicapped daughter. One question stands in her way: Is she really Caroline?
IMDb synopsis 2:
Set in the 1950s, a woman (Zimbalist) appears 14 years after supposedly dying in a plane crash. She claims she never boarded the plane and simply used the crash as a means to escape her débutante life. Now, she is ready to rejoin the rest of the family, except everyone is skeptical particularly as she has shown up just in time to inherit a fortune from a recently deceased grandmother (Dorothy McGuire shown in flashbacks).

Caroline? (TV Movie 1990) - IMDb (http://www.imdb.com/title/tt0099225/)