The only response to “I’m sorry” is “thank you,” because “I’m sorry” is such a flimsy response to death. So is a casserole, or a hug–do you really think that what she needs, right now, is another hug?
But of course such gifts are not really for the grieving.
This is the only appropriate gift for a widow: a minute of your life. A minute you would have spent breathing and loving, with your eyes open, warm. A minute from your long and many days, to bring your death that much closer, and let the two of them say goodbye.