The Daughter of the Serpent King

Her father died when she was seven, poisoned. She was then raised with her two brother's by their mother. Now they're eighteen, sixteen and Diane fourteen; As the youngest she isn't mentioned for a throne. When she gets in a relationship with him her mother and eldest brother's have other plans for her including a throne and marriage, Diane would risk being exiled for him, but would she risk her life as well?