What I meant by " women like Sheila " ,was to point out that looking at Sheila's photo,you wouldn't suspect that anything was amiss,which is the same as a lot of women like her,,,,slim,,,attractive,,,,a family,,,but behind that facade lies something that none of us can predict if we don't know that person,,until something happens that appears to be " out of character ". Then the disbelief kicks in.
It's all too easy to be in denial that women can be so cruel,,but there you have it. Unless you've worked among such women,then you have no concept of their behaviour.