What should I Tell My Friend About Losing Somebody Important?

I have a friend and she lost her sister a few years ago tragically. Lots of the time she gets very depressed and I don't know what to tell her. Her sister was sort of close to her. Sometimes she gets depressed to the point she wants to commit suicide. Over top of losing her sister her mom is in the hospital and is not expected to make it. I need help on things I could tell her to comfort her when she starts thinking of her family members.