Yes. Massive haemorrhage will delay post mortem hypostasis because so much blood is lost. This does not apply to Sheila or June (Obviously) despite June taking three times as many bullets as Sheila.
But you never fail to find an excuse for things 
The difference you fail to acknowledge is this. EITHER one of the two shots to Sheila would undoubtedly have killed her, a shot to the jugular, the first, causing a massively substantial/substantially massive haemorrhage taking a little longer but ultimately having the same outcome as the second, a shot to the brain, although there is no clear indication of how long there was between shots. Only one of the many body shots sustained by June would have caused her death, none causing her to haemorrhage.