Can my 81 year old grandmother be able to function normally as she is on a ventilator, suffers from pericardial effusion, kidney failure and cancer?

End of Life: I am very sorry to hear of your grandmother's troubles. It must be very hard for you. Miracles do happen, but it sounds like your grandmother is nearing the end of her life. These days when she is so sick may become treasured memories for you as you and your family get to be with her and to talk to her and to tell her how much she is loved. Let's let the rest be in god's hands for now.

Unlikely: That constellation of symptoms portends a very grim prognosis. The likelihood of independent recovery is unfortunately quite low and risk of death very high combining these conditions together.