When the car crashes there is snow on the trees and ground, but when they are brought to the hospital and Mia looks out the window, there is no snow and it looks like spring outside.
When Mia finds out that Teddy has died, she seems to undergo some physical trauma. One of the nurses notes that her pulse oximetry levels are dropping. However, when a person is on a ventilator (as is clearly depicted) their oxygen levels remain at above 99%. It is anatomically impossible for them not to.
Mia wanders barefoot around the hospital halls as a ghost, but in some angles, the soles of her feet are darkened and soiled, most probably by the dust/dirt of the hospital floor.