My SIL died several years ago after a 10 yr bout with cancer. She and her husband had been married for over 40 years, but we knew she would never make it to 50 years. So I made a memory quilt for their 45th Anniversary and they enjoyed it for a few years. But it has been in a box for several years now, somewhere..... I do not know if it will ever be enjoyed again, but not in her husband's lifetime I'm sure.
I'm telling you this so that you might understand that everyone handles grief in their own way, and some never even recover. I agree that a memory quilt now may not be the best idea (and it may never happen), but a small quilt for your SIL would be nice and it will help you too! Sorry for the family's loss.