Total fiction! Sheila never attacked anyone.
Refer to the pathologists trial testimony - somebody 'had grabbed' June Bamber by the throat', noe 'those marks' on Junes neck and the 'top part of Sheila's right hand' are 'a perfect match', so there can be no 'mistaking', who did what, and in any event 'why was Sheila trying to throttle her mother'?
Me thinks I know the answer...
You think whatever you like, the evidence is 'overwhelming', Sheila had not only shot her mother, but she had tried to throttle her, the corresponding hand marks on Junes throat, and the bloodstained marks on the top of Sheila's right hand, being 'all the evidence' required to prove an association between both parties, who must have been at conflict with one another, just before June Bamber had been killed. At that time, Sheila's actions being a telling factor in the role she played in her mother's death...