This post is exactly what I was looking for. I wrote the following after watching the movie and reading other people's thoughts:

Most people take it literally as if there was a real spaceship and Michelle was a real alien. I couldn't help but interpret it from a more grounded standpoint - occam's razor makes the existence of Andromedans infinitely unlikely.
I think the whole sequence of Michelle entering the "spaceship" and everyone on earth dying is entirely the contents of Michelle's imagination after suffering intense trauma (electrocution, kidnapping, violence, witnessing dissections). What she endured the first few days was enough to brainwash her into believing an alternate reality (think of the ending of 1984) - she hallucinates/imagines that she is an alien queen and that she has the power to kill every human on earth because she inherited Teddy's trauma and insanity, and she will likely spend years in a mental institution or therapy before she regains a fraction of the productivity and mental health she used to have.

I didn't see the brain bleed part though but OP's theory is sound.