She described her role as that of a...
= She described her role as the role of a....
that作替代词,再比如
The weather of Beijing is colder than that (=the weathe)of Guangzhou. 北京的天气比广州冷。
He Ruixian, a young actress who plays Ling, describes her role as "straightforward, brave and intransigent", that of a brave heroine who battles against societal bias to pursue her culinary dream.
饰演凌小小的年轻女演员何瑞贤认为,她饰演的角色“直率、勇敢、不妥协”,是一位勇敢的女主人公,她与社会偏见作斗争,追求自己的烹饪梦想。
这是一段来自China Daily的一篇介绍《珍馐记》古装剧的文章。
想请问,这里的“that of a brave heroine…句末”这个我认为是同位语成分的内容,其中这里的that是什么用法呢?