Yes a very good point, it occurs after 3 hours and is most pronounced after 12 hours before subsiding again after 72 hours.
There's also liver Mortis to consider, which seems to be present in June but not Sheila, not that I'm an expert in photography of course.
Another consideration is could she have been incapacitated but not immediately killed from the two gunshot wounds, succumbing to death much later than being shot or shooting herself.