Hi Nugs 
Its not really relevant whether anyone saw Sheila with a gun. Sheila had lived around guns most of her life and it would not be beyond reason that she could have used any gun/rifle that was on the farm. Its a bit like a farmer living on a milking farm and not knowing how to milk his cows. Well.not quite the same Ha!
Loading and shooting a gun/rifle does not require an A'level nor is it restricted to only a male can use them. We all heard what the rifle expert said in relation to rifle 18....the recoil is so small a child could use this rifle.
For anyone to think that its not within the realms of possibility for a woman to load and fire a rifle is a little bit out of touch. It is possible and not impossible that is what I am trying to say. 
Once again the same oh she lived on a farm she had to be around guns. Being in a house with guns doesn't mean you know how to use any let alone all of them.
Lynette Fromme grew up around guns and she didn't even know she needed to chamber a round:
"As Ford drew near, Fromme pulled a .45-caliber semiautomatic pistol, aimed it at the president and pulled the trigger.
Witnesses nearby heard the "click" of the hammer dropping. Secret Service agents later found that the pistol had four rounds in its magazine, but the chamber was empty.
Agents swarmed Fromme and wrestled the weapon from her hand as she shouted, "Don't get excited! It didn't go off! It didn't go off!"
http://www.sfgate.com/nation/article/Would-be-assassin-Squeaky-Fromme-is-paroled-3221893.phpThere is no evidence she used any guns at all but certianly not the murder weapon or a gun like it. Not knowing she needed to chamber a roudn let alone how would result in the same fate as Fromme, having it taken away without doing any harm.
You grossly underestimate how much knowledge is required to operate a weapon. Many wepaons have safeties as well.
The fact she payed no interest to weapons menas she would be unlikely to go for one if she wanted to arm herself instead being likely to go for something she used in the past like a pot or pan which is the weapon of choice for women- moreso than knives. Women in a kitchen tend to grab pots and pans more than they do knives.
She certainly would not be likely to load 11 rounds which is what was fired in the initial hail in themaster bedroom. That is a clue it was Jeremy. Another clue is the staging of the bullets in the kitchen. She would not have used 20 bullets from the bullets in the kitchen then ran to the closet to get 5 more when there were still 30 in the pile she was using.
