……a dear old lady who had always been so kind to everybody, had，in her youth,poisoned every one of her five husbands.
这个句子中的had使用方法不太了解，怎么样理解？谢谢
a dear old lady （who had always been so kind to everybody）, had（，in her youth, ）poisoned every one of her five husbands.
目前看清楚没，主语 a dear old lady, 谓语动词 had poinsed ...
in her youth是插入的状语，所以用逗号隔开。
had一个词，如何能是插入语呢？提问之前自己先要想一想。