1. From the moment Mary Stuart arrived in Scotland at the age of 18 from the French court where she had been brought up, the relationship between the cousins was tainted with mutual suspicion.

结构剖析：这是一个简单句，主语是the relationship between the cousins，谓语是was tranted with mutual suspicion，from the moment Mary Stuart arrived in Scotland at the age of 18 from the French court where she had been brought up是介词短语做时间状语。

在主语中between the cousins是介词短语修饰名词relationship；在谓语中was tranted是使用了被动语态；在介词短语中含有两个定语从句——Mary Stuart arrived in Scotland at the age of 18 from the French court where she had been brought up。定语从句中at the age of 18是做时间状语，from the French是介词短语做地点状语，注意语序问题，表示时间的状语位于表示地点的状语。

这个定语从句由关系副词when引导修饰先行词moment。在这个定语从句中又含有一个由关系副词引导的定语从句——she had been brought up，它修饰先行词court。

2. At the first opportunity, Elizabeth behaved badly, almost irrationally, denying Mary safe conduct through England to her new realm and forcing her to sail the long way round to Scotland.

结构剖析：这个句子是含有2分词短语的复合句。第一分词短语是——denying Mary safe conduct through England to her new realm，第二个分词短语是——forcing her to sail the long way round to Scotland，这2个分词短语由并列连词and连接。这2个分词短语都做方式状语或者也可以成为伴随状况状语。

3. Though very much the injured party, Mary's response already betrayed the theatrical self-pity which so got up Elizabeth's nose.

结构剖析：这个句子是个含有定语从句的复合句。主句是——Though very much the injured party, Mary's response already betrayed the theatrical self-pity，从句是—— which so got up Elizabeth's nose。

在主句中，though very much injured party中的injured是过去分词作定语修饰party，注意party在这里是“一方”的意思，副词性短语very much是修饰injured这个形容词。

定语从句是由which引导，因为先行词是self-pity，它在定语从句中做主语，指代事情，那么可用的关系代词which和that都可以，做主语关系代词是不能省略的。