1. which 的先行词是to make people feel at ease（让人们放心），也就是说，which 指代不定式的内容。千万不能指inability，也不能包括inability。trust 是信任，与之匹配的先行词是不定式，而不是“无能”。

2. that 引导trust 的同位语从句。

3. given 是“分词介词”，表示“原因”，本句意为“鉴于；考虑到；因为”。

She gave up the only form of soft power at her disposal, given her inability to make people feel at ease, which was trust that she would do the right thing.

【翻译】她放弃了唯一可以支配的软实力，因为她不能让人们感到放心，即人们对她做事正确的信任。