What is it like if a mouth is like "cupid's bow" and "unformed and generic"?

Could anyone help me in understanding the following expression?
What is the mouth like if it is "like a cupid's bow" and "as unformed and generic as a baby's"?
It's from a novel. 13 year old girl is frightened and crying to find her close friend is dead.

Following is from the novel:
Then she (13 year old girl) put her hands up to scrub at her eyes with her palms, a toddler move. Her mouth was still a cupid's bow, as unformed and generic as a baby's.

Your assistance would be highly appreciated.

The cupid's bow is the line of the top lip - see here for one http://www.slowburning.com/store/med...l-jester12.jpg

Babies' mouths show this particularly.