Who's Betty Schaefer? (US 1994Musical "Sunset Boulevard")

NORMA: Is this what youre looking for, by any chance?
JOE: Why, yes
NORMA: Whose phone number is this?
Ive been worried about the line of my throat.
I think this woman has done wonders with it
JOE: Good
NORMA: And Ive lost half a pound since Tuesday
JOE: Very good
NORMA: Now its after nine. Id better get to bed
JOE: You had
NORMA: Are you coming up?
JOE: I think Ill read a while longer
NORMA: You went out last night, didnt you, Joe?
JOE: I went for a walk
NORMA: You took the car
JOE: I drove to the beach
NORMA: Whos Betty Schaefer?
JOE: Surely, you dont want me to feel as if Im a prisoner in this house?
NORMA: You dont understand, Joe.
Im under such a terrible strain
Its been so hard I even got myself a revolver.
The only thing that stopped me from killing myself was the thought of all those people,
waiting to see me back on the screen.
How could I disappoint them?
All I ask is a little patience, a little understanding
JOE: Norma, theres nothing to worry about. I havent done anything
NORMA: Of course you havent. Good night, my darling
JOE: I should have stayed there
Poor Norma
So desperate to be ready
For what would never happen
But Betty would be waiting
We had a script to finish
One unexpected love scene
Two people, both risking
A kind of happy ending