She did wake. The blood on her night dress shows she was sitting up when one of the shots were fired. There was blood on her hands, if you look at the high resolution photos from the sky3 program you can see it clearly along with her bloody fingerprints on the night dress , you can also read Vanesiz original autopsy were he writes the palm of her hand was bloody.
There is no blood on Sheila's bed or the room she was sleeping in that night. the above theory is impossible
She may have been sitting up for the first or second shot.
Bamber may have pulled a sleeping Sheila into a sitting position when she was in bed. To get a good aim. That would not be hard.
Or his second shot in the main bedroom she may have been sitting up. The 2002 appeal report said Sheila's legs were pulled after the second shot.
There is no reason why there should be blood in Sheila's bed. If she was sitting up and then carried away straight away. Nothing would drip down.