Complex sentence: She is very protective of Aria, being the keeper of the key to her chastity belt, and seems to have a fetish for anything that Aria has touched or worn, as well as unwashed underwear in general.
Split into simpler sentences: She is very protective of Aria, and bears the key to her chastity belt. She has a fetish for anything that Aria has touched or worn, as well as unwashed underwear in general.