Science has an answer
Even though Tina had her own explanation of what she saw, and how it connected to the same images she saw as a child, science has a different answer. People that have near-death experiences, usually hallucinate and see things. Nothing can really be confirmed, but the brain does do odd things.
Even after the heart stops beating, it has been proven that the brain still keeps functioning for a short period of time. During this time, the brain may go to a different state or see something in a new light. That may explain why Tina saw, but how could she have seen the same thing as a child?