I'd have to be capable of writing that long of a monologue in the first place. I believe that after I did, the proper sentence and emotional response would come forth from the brain to the blank page automagically. Hopefully a PEBKAC error won't take place ;)

Interesting that Birdman has several long monologues from a variety of characters. Of course, this being a movie about a stage play, there's a kind of symmetry there as plays often have long monologues. Nothing wrong with monologues as long as they are in character, reveal character, and are as entertaining as hell.

The bitter truth of Sams words hit Riggan like a wall of devastation. A crushing silence. Guilt trickles over Sams face as she takes in the impact of her verbal tirade, all she can do is leave.

There you go, Stevie B. We have the right to comment on the moment in scene description if we feel it will drive home something important to the reader. We have to be judicious. For some readers, what is in the shooting script for Birdman may work as is, the effect of Sam's tirade enough to carry forward into the minimal description of her response. However there's an argument to be made to give the reader more, as with your description. It's a tricky business and all we can do is follow our instincts, write what we write, get some reads, and see if this or that description is too much, too little, then rewrite and rewrite. Thanks for your take!