J.R.
Hi M., Let me start by saying that I am very sorry for your loss. I made my mother a scrapbook for Christmas the year my Grandmother passed. I filled it with photos and other items from my Grandmother's life. It brought my mother to tears when I gave it to her, but in the following days (and even now, 5 yrs later)she looked through the book and laughed and shared stories with us about my Grandmother that no one ever knew. It's a nice way for my kids to get to know my Grandmother also (they are 10 and 4). Since you said you like to scrapbook, maybe you could do something like that. Also, ask your SIL's friends to help out by writing little stories they remember about your MIL while they were growing up and add them to the book. I hope my suggestion helps and if you decide to do it, you get to know your MIL a little better, not only as a mom, but as a fellow woman. Good luck.
Jennifer