When my friend's baby died after being born preemie, I gave them a tree to plant in their yard. They loved it. But fabric- fancy's idea of bricks/benches for a bereavement memorial is a wonderful idea.
Please tell her we're keeping her in our prayers, and you are a good friend. I lost my first to a very early miscarriage, but have been blessed with two healthy (now adult) kids. I am blessed.