The calm has been explained in multiple articles as a well known survival mechanism. When the immediate danger has passed and her daughter is being cared for by someone else, that is probably when it will hit her.
I was going to say that you'd hope the police would understand that once it's on facebook odds are that it has been duplicated for 'backup' purposes and is recoverable. Just deleting it from the profile is not enough but I am guessing they weren't thinking clearly. Tampering with evidence, they really do have no where left to run.