My sister in law is in a coma from ODing will she wake up?

My sister in law has been in a coma for 6 days now. She OD-ed on 100 tegertol . She is breathing on her own but has a ventilator to keep her air way open.she does not respond to pain or talking to her. The doctor said she has no bleeds in the brain. and she is starting to swell up. she also has epilepsy and has been taking mive seizures regularly. the doctors think she may have brain damage. Please pray for her to wake up she is not only my sister in law but my best friend too. What are the chances of her waking up none seems to know not the doctors or the nurses.