When, how did she come up with the idea of Max being smothered?
Purely a guess by me...Max's injury stetched his spinal cord so he was unable breathe to causing him to suffocate. When he came into the ER, I would imagine he looked similar to a child who had been suffocated, maybe blue lips? I am just guessing here
And the ER doctor might not have sat Dina down and said I think Max was suffocated. He could have been listing Max's injuries and said something like, "XYZ is similar to what we see in children who have been suffocated." It could have been more innocent than we are guessing.