这不是完整的句子 是一个原因状语从句
这也许是上句的状语从句
since 是从属连词 引导状语从句
her parents 是从句中的主语
had impressed 是谓语upon her是状语
后面是宾语从句作had impressed的宾语
其中that是连接词引导宾语从句
it是从句中的形式主语 would be 是系动词unforgivable是表语
to miss it and cause the friends with whom she was going to stay to make two journeys to meet her是不定式短语 作从句中的真主语
其中.to miss it and cause the friends 是并列的不定式短语
with whom she was going 是定语从句修饰the friends
to stay to make two journeys to meet her是不定式宾语the friends的宾补
其中 to make two journeys to meet her是to stay的目的状语
其中to meet her是to make two journeys的目的状语
句子意思 因为她的父母再三跟她说,如果误了这趟车,她的东道主朋友就得接她两趟,这是不应该的.