Sheridan Le Fanu 
Carmilla [PDF ebook] 

Isolated in a picturesque but remote castle deep in a Styrian forest, Laura spends her days with her family, longing for a companion her age. Her wish is granted when a carriage accident outside her home brings a girl her age into the family’s care, and the two — recognising each other from dreams seen years before — become fast friends. Though they get along well at first, the stranger’s eccentricities slowly become cause for concern, as do the murders that begin to plague the towns around them…