So you are saying she didn't do everything in 40 minutes. Agreeing with my thread post.
Do you think having nice nails was important to Sheila after the massacre?
Why did Sheila wait until the police entered before shooting herself?
Sheila's nails look freshly painted in pictures I have seen that's all I can say, why did she delay shooting herself? again this is very common.
Please have a look at murders committed by people with paranoid schizophrenia, you will see many similarities to this case, children often involved and a severe beating for example.