I have to say that I felt damn sorry for Sheila,she'd had all she could tolerate and simply " lost it ". When you reach the point of no return such as she clearly did,there doesn't seem to be an end to it on the horizon and she didn't have the strength of mind to carry on. You don't have to be suffering from schizophrenia or any psychotic illness to experience such a feeling. Nobody knows what goes on in, or with the mind.