Complex sentence: Frustrated with Tenzin and her father Tonraq for keeping her in the compound of The Order of the White Lotus when Aang wanted otherwise, she chooses Unalaq as her new spiritual teacher, saddening Tenzin greatly.
Split into simpler sentences: Frustrated with Tenzin and her father Tonraq for keeping her in the compound of The Order of the White Lotus when Aang wanted otherwise. Because of this she chooses Unalaq as her new spiritual teacher, saddening Tenzin greatly.