It was surprising, because her acting seemed not so important to the piece as his.

"It seems like a lot of money for what you have to do," he said.
"There," she smiled warmly, "didn't I always say you were a natural-born trouper?
Well, it is a lot of money for me, but you see I've helped Jeff dope out both of these pieces.

I'm not so bad at gags--I mean the kind of stuff he needs in these serious dramas.

This big scene of yours, where you go off to the city and come back a wreck on Christmas night--that's mine.

I doped it out after the piece was started--after I'd had a good look at the truck driver that plays opposite you." Truck driver?
It appeared that Miss Montague was actually applying this term to the New York society girl who in private life was burdened with an ailing family.