Which of course is very strange, as most of the residue is expelled from the muzzle end of the gun. If that is so and it IS so then it is logical that Sheila could not fail to get residue on her. So forgive me in thinking that they were not being very truthful on that one.
1) you are ignoring that PGSR and soot are expelled through the ejection port and vents (those holes adjacent to the ejection port which exist for gases and PGSR to escape through). That is how the shooter gets PGSR and soot on their hands and clothing and after 25 shots would have a good amount on them. Hugging the weapon as she fired would have resulted in PGSR and soot on her gown.
This photo is from the photo section of this website

2) you are ignoring that her fatal wound was a soft contact wound so how would GSR get on her clothing if it was propelled directly into her wound?
Her not-fatal wound was determined to be either a soft contact wound or close contact which means the distance between the barrel and her neck was not much so the unburned gunpowder would go mostly in and around the wound. Unburned powder gets less concentrated the further the gun is fired from the victim. Use a flashlight to simulate it. Stick the flashlight against the wall to simulate a contact wound. Now move it away. The further away the bigger circle on the wall. It would have to be fired at a good distance for the cone of unburned gunpowder to extend to her gown when shot in the neck. She wasn't shot from far enough away for that to happen. Had she been shot from far enough away for unburned powder to get on her gown from either shot then that would be ABSOLUTE proof she was murdered because her arms are not long enough to hold the gun that far away.
In case you can't read the print it states:
"A loose contact wound results when the muzzle end of the weapon is not pressed firmly against the body, but instead is held loosely in contact with the body at the moment of discharge. Such wounds are characterized by a wide, yet desne, deposit of soot encircling the central perforation, and the absense of significant searing, obvious muzzle imprint, or significant powder tattooing. If powder tattooing is present, the tattoo marks or grains of gunpowder are usually within the ring of soot."
"By definition, near contact gunshot wounds occur when the muzzle of the weapon is held near, but not in contact with, the body surface, and yet close enough that significant powder tattooing does not occur."
A photo of sooting:
http://library.med.utah.edu/WebPath/TUTORIAL/GUNS/GUN004.html