Who is Galanna from The Hero and the Crown and what is their importance?

Galanna is one of Aerin's cousin. Galanna is a beautiful girl, small and petite, where Aerin is tall and clumsy. Galanna has always wanted to marry Tor because he is destined to be king. However, Tor never shows interest in Galanna. In fact, Galanna can see from an early stage that Tor has eyes only for Aerin, fueling her dislike of Aerin. Galanna often teases Aerin, often telling her that she is not of royal blood and does not deserve to marry a man like Tor. It is also Galanna who encourages Aerin to eat the plant that leads to a near fatal illness and dulls her blooming magical powers.