Help grandma on ventilator... !!!?

My grand mom is 72. She is suffering from heart disease from last 6-7 years .. Doctors cannot perform surgery on her because she is diabetic . Few days back she was having trouble in breathing so she has been hospitalized . Last night her heart collapsed n she had been on ventilator since then. Her body also swelled.and doctor is saying they have to do bypass surgery now. Is it possible??? We r having doubts on doctor that he's only making money and my grand mom is more. Plz tell me how to tell if a person is dead or alive while on ventilator???