The grandmother is of course a tragic figure in that she has to cope with the loss of so much in her life; not only her sister and family in Dresden but also the loss of her son in his adult life and then the abandonment of her husband, who walked out leaving her pregnant. In addition, she had to live with the fact that her husband was more in love with her dead sister than he ever was in love with her. However, note what her husband writes to his son about his abandonment of her and her character:
I can't live. I've tried and I can't. If that sounds simple, it's simple like a mountain is simple. Your mother suffered, too, but she chose to live, and lived, be her son and her husband.
The grandmother of course finds it very hard to face the loss of her husband, but, as her husband himself identifies, she is a survivor who chooses to live no matter what the hardships that face her. Unlike her husband, who can't seem to accept life because of the weight of tragedy that lies on his shoulders, she is able to continue living with determination. It is clear that this resolute nature comes in part from the knowledge that at the time of her abandonment she was bearing their child in her womb, and therefore she chooses to live in part for him, just as she chooses to live after her son's death in part for her grandson, Oskar.
Clearly these are two seperate cases.
With Grandma's lost of her son, Tom Jr., she gets cautious and so she and Oscar for example constantly talk via phones and Oscar says "I'm OK" to reunsure her.
With Grandma's lost of her husband, Tom Sr., she feels alone, and lucky she has a son a few months later to be there for here.
Grandma also loses her sister, Anna, and her family in desden.