If I didn't know better I'd think you were talking about the end of Brit flick "Descent."

Or are you?

If you are then to understand the ending you would need to go right back to the start, as I said the film has several layers and several interpretations, as far as I'm concerned the film switches mode when she wakes up in hospital after the accident, from then on you need to clarify fantasy from reality. 

Cheers Trev