why did she not use the rifle to beat her.make no mistake some one used it on nb to give him a awful beating in the kitchen,black eyes,broken nose and other injurys 
After much contemplation, I have come to the conclusion that either at the time Sheila was shooting her mother who was in bed (first episode of 5 shots) that Sheila (a) thought that she had killed her mother, or (b) that Sheila was interrupted in what she was trying to do by her dad appearing in the bedroom?
If hard pushed I would be inclined to believe that she got interrupted as per scenario (b)...
So, she fired a shot or two off at dad...
Dad darts off downstairs to the kitchen phone, and Sheila fires a shot at him whilst he makes off down the main stairs. She eventually pursues him downstairs into the kitchen. By the time she enters the kitchen, dad has already made the very brief call to Jeremy, and he has started talking on the phone to the police at 3.26am. Sheila has four or five live rounds still in the rifle, and she manages to fire all four or five rounds off, killing dad outright. When she is out of bullets, she proceeded to hit dad with the empty weapon...
During this episode she prods dad with the muzzle end of the anshuzt rifles barrel, and jabs him on the back of his neck after warming the muzzle in the aga...