Thinking of your friend and also you and your DD, so sorry for your loss.
I know the poem you mean MrsMom if I come across it I will send you a link, my cousin lost her son in February and I sent her this poem that she found a comfort. It basically says that the length of someone's life is not what counts, it is by Ben Jonson and is called Proportion, perhaps you could share it with your friend when she is ready:
It is not growing like a tree
In bulk doth make Man better be;
Or standing long as oak, three hundred year,
To fall a log at last, dry, bald, and sere:
A lily of a day
Is fairer far in May,
Although it fall and die that night?
It was the plant and flower of light.
In small proportions we just beauties see;
And in short measures life may perfect be.
I lost my DH in June, and my youngest was very comforted in the immediate aftermath by a special cuddly called a Shining Star that came with a certificate to name a star. We bought it at Woolworths, but I haven't seen them there again. When your daughter is ready, a memory box might prove a comfort, she will never forget her friend, but when people are first bereaved they often fear that.