The Scene that Most Annoyed Me (Spoilers)

You never know what you or anyone else would do in that situation until you're in that situation yourself. "Paralyzed by fear" is a real phenomenon that some people experience. It could have been that she was so terrified she literally couldn't move. Also, keep in mind - you as the viewer can see what he's doing but she is hiding under the bed with her back turned to him and has no idea what he's doing. Yea, she knows he's hitting the wall but doesn't know if he's looking for anything within the wall, or how intently he's focused on the wall. For all she knows, by the time she crawls out from under the bed he will see her and jump on top of her.

Several scenes in this movie were annoying but that wasn't one of them.

I wondered the same thing while watching. That was her chance. But it's easy to criticise while you're the one watching. I'll bet a large percentage of people would be frozen with fear.