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.
(..) is that... I know what I want for my birthday, now. And what is that? New paint. That paint made from the white shells you once brought me. Well that is a very long trip, Rapunzel. Almost three day's time. I just thought it was a better idea than, uh, stars. (..)2010 Tangled