Who is Antonia Owens from Practical Magic and what is their importance?

Antonia is the eldest daughter of Sally Owens. Antonia is known for her looks and is decidedly spoiled and always has something mean to say to her sister. Antonia begins to feel less attractive when her sister turns thirteen and begins to look like a beautiful woman. Antonia and Kylie are not able to get along until Antonia comforts Kylie after some men threaten to rape her. Antonia realizes later that a person's attractiveness is relative to their frame of mind.