We don't know where Grell Sutcliffe was when she fell asleep, do we? All of the locations on the upper floor, save the elevator bay, were occupied, meaning she wasn't there. She may have been somewhere else, but her own room is a possibility.

If someone targeted her, it means that she somehow fled up two floors and chased into the tea room and up a tightrope before she was killed.

On the other hand, if Grell came to the upper floors at her own leisure and targeted someone who successfully fended her off, wouldn't that make a little more sense?