Of course she would have woken up, no way could he have carried her to the main bedroom put her down and shot her while still asleep, makes no sense at all, neither do I believe she would have walked there/been led there without any attempt to get away from him. She either killed herself or JB shot her once in the neck, catching her unawares and then positioned her on the floor and shot her again leaving the rifle on her and setting the scene (badly) as a suicide.
Well he had to pick up a light woman for about 10 seconds. Carrying her a few feet.
It is doubtful she would wake in ten seconds. If she started to wake, there is no way she would know what was happening, or going to happen. Before it was too late. Brothers shooting sisters is rare.