Making new friends helped her 'come out of her shell'. = Making new friends 'brought her out of her shell'.
He lost confidence in himself and 'retreated/withdrew into his shell'.
The police found several spent 'shells' at the scene of the shooting.
(..) May l? "As I ate the oysters with their strong taste of the sea... and their faint metallic taste... as I drank their cold liquid from each shell... and washed it down with the crisp taste of the wine... I lost the empty feeling... and began to be happy." He never forgets to describe (..)1998 City of Angels