Book 6 in the SF/F series Children of The Dragon by T. M. Moore.
Charity Rakham is a young English girl who learns about womanhood the hard way when her father and fiance' are killed by the dread pirate Blackbeard. Sold into slavery, she becomes a maid to a woman of means who is murdered, and she is framed for it. Now a fugitive, she rescues a hostage of the king of thieves who offers her love and the dragon's blood. Charity gains justice when she becomes the captain of the most fearsome pirate ship on the Caribbean Sea.
Never underestimate the power of love.