What the River Knows by Isabel Ibanez

Inez Olivera is a Bolian-Argentinian living in Buenos Aires in the 19th century.  Inez's parents are mysteriously killed leaving her in the guardianship of an Egyption brother-in-law.  There, Inez travels, taking with her a ring full of old world magic.  Inez discovers the world of old magic hoping to uncover the truth about her parent's death.