I'm sorry for your friends loss. I, too, think you should wait much, much longer before you approach her about doing this, and perhaps even wait for her to suggest it herself.
I lost my father when I was 16 and my husband when I was 22, and would find a quilt made from the clothing of either to be something I would hold so 'sacred' I would never use it. It would be put away in a very safe place and rarely see the light of day. I don't think that is what you want to happen to something you made to help ease her pain, so please be sure it is something she really, truly wants you to do. It will be quite a long time before she will be able to know if it is.