No marks,,,,no blood on Sheila.
Firstly,Sheila would have relied on the rifle butt in which to render her father incapable, after a good bashing.Don't forget,because of a person's " slight build ",especially in a female, doesn't always mean that they're physically unable to put up a fight with someone stronger providing that they've got some sort of a weapon in which to give a greater impact/injury. Sheila,in view of her unstable condition,would have had the strength of an ox enabling her to deliver the blows on her father that she did.
Nevill,being the gentleman that he was,and confronted by his daughter in her state of mind,was more than likely trying to release the rifle from her without hurting her ( which would account for a lack of marks/bruises,etc on Sheila ),but because Nevill was overpowered by her as she pumped shots into him,he would have finally died.
The blood would have been mopped up by Sheila,using her knickers ( because she was found dead,minus them ) and would have also used the same garment for mopping up any blood,or wiping it from her own body. The knickers were then put into a bucket of water,which by the way was never tested to find out whether it was menstrual blood or otherwise.An important issue that appeared to be overlooked and one which the police seemed dis-interested in. One person who was interested in it was AE,who took the bucket,complete with garment,back to her home. Why was that,I wonder.? It happened to be quite a vital piece of evidence to me. Think about it. By all accounts,it was quite " bloody ",which, could well have been venous blood as opposed to menstrual.
Another fine mess by the Clouseau gang.