Thanks for the information. I like the fact she liked the movie.

The guys on Garboforever wrote this:
DID GARBO SEE THE FILM ?
One of Garbo's closest friends, the art dealer Sam Green, said
I know she didn't see the movie, because I was the one who sent her a telegram saying, There's a film called Garbo Talks' in New York, and they'll be making a fuss. Don't come back until the run is over in two weeks.' And she didn't.
But a few years later, Garbo told composer David Diamond she saw the movie on TV and liked it:
She loved Harvey Fierstein in it but she wouldn't go to see him in Torch Song Trilogy',
Diamond recalled.
http://www.garboforever.com/Garbo_Talks.htm

I don't think anyone will ever know.

I read somewhere that she was offered the part first and she obviously declined. Wether she liked it or not some sources say she did, others that she never saw the film.