I remember seeing a movie in the late 70's early 80's that was about a
haunting of a house.  The ghost was a little southern girl who had
been killed by her uncle, I believe.  She had diamonds hidden away in
one of her dolls.  It was on TV.  I believe the house was a southern
plantation with the name of belle something or other.

Hi sweetzies,

I believe the movie you are looking for is called 'Child of Glass'.

From an Amazon user review:
"This movie begins showing The Ainsworth family traveling to their new
plantaion house. When they arive the Kids are pretty shocked at how
run down the house is. Well they work on it. And you meet the Drunk
Caretaker who has Murder On His Mind. One night Alexander sees a Blue
Light from the hay loft of the barn. He goes out there and sees the
ghost of Inez. She tells him what help she needs from him. Well
Alexanders decides to help him. I don't remember the exact riddle. But
it was about the 2 should touch. Well it goes on. And Alexander falls
into the well. And he is found. His parents send his little friend
Blossom down. And she finds the China Doll. They rescue Alexander and
they go into the Cemetery into the Chapel of Inezs Family and place
the doll on top of her tomb. Well the gost of Inez apperas and grabs
the doll than dies and evaporates into the Tomb. Than the doll appears
and falls onto the floor. The head shatters and in side the head is
the long lost treasure. Which consists of millions of dollars worth of
diamonds."

http://www.amazon.com/exec/obidos/tg/detail/-/6300276368/


Here's a description of someone else looking for this movie:
"My sister and I were trying to remember the movie from the late 70's,
I thought it was a Disney movie of a little boy who befriends a girl
ghost (french accent) which leads me to believe it was filmed in
Louisiana whose spirit cannot rest until her murder is solved. She
constantly signs this little french song. THe mystery is she was
chased into a well and dies her doll being trapped within the well.
The little boy also falls into the well when being chased. He grabs
the doll and when the doll breaks open the diamonds fall out. Thus the
little girls murder is revealed and her spirit is released..."

http://www.leisuresuit.net/Webzine/articles/70s_cultmovies.shtml


From the Internet Movie Database:

Child of Glass (1978) (TV)
Directed by: John Erman
Writing credits: Richard Peck (novel)
 
Plot Outline: A boy continues to see a ghost of a Creole girl and he
has to help her solve a riddle...otherwise he might be haunted for the
rest of his life.

http://www.imdb.com/title/tt0077325/


Search criteria:
movie diamonds hidden "her doll"
site:.amazon.com movie doll ghost girl 
"Child of Glass"


I hope this is helpful. If you have any questions regarding my answer,
or believe this is not the movie you remember, please don?t hesitate
to ask for further assistance before rating.

Best regards,
Rainbow

This was it exactly!  Thank you so much!  I had spent so much time
trying to find out what it was by putting key words into search
engines and had come up with nothing.  Thanks again!