The Very Nearly Honourable League Of Pirates "Magic Marks The Spot" by Caroline Carlson

All Hilary Westfield wants is to be... a pirate. There's only one problem: The Very Nearly Honourable League of Pirates refuses to let any girl join their ranks of scourges and scallywags.

But Hilary is not the kind of girl to take no for answer. To escape a life of petticoats and politeness at her stuffy finishing school, Hilary sets out in search of her own seaworthy adventure, where she gets swept up in a  quest involving a map without an X, a magical treasure that likely doesn't exist, a talking gargoyle, a crew of misfit scallywags, and the most treacherous—and unexpected—villain on the High Seas. 

I really recommend this book and its sequel: The Terror Of The Southlands along with Book 3: The Buccaneers Code.