Bad Acting - Blind?

One of the biggest issues I had with this movie is that Michelle Monaghan couldn't act blind! The first time I noticed it was when she thought Chad & Hollander had left, and was LOOKING at Ryan's body.

A blind person wouldn't be tuned into where the body was with their gaze. My husband tried to pass it off by saying that she was sighted until adulthood, so maybe some behaviors stayed with her. I was willing to concede this, UNTIL...

Keaton's character throws the cat off the roof... and what does Sarah do? Runs to the ledge & looks down! Seriously? Was this a bad directing choice, an oversight, or just an actress who kept losing her character??