The girl arranged to have piano lessons at the training centre with her sister _______ she would stay for an hour.

我把这个句子中with her sister 换一下位置，你就明白用where 引导定语从句了。

1. The girl arranged to have piano lessons with her sister at the training centre _______ she would stay for an hour.

2. The girl arranged to have piano lessons with her sister at the training centre where she would stay for an hour. （把with her sister 提到前面去）

3. The girl arranged to have piano lessons at the training centre with her sister where she would stay for an hour. （再把with her sister 还原回去）

【分析】

主句：The girl arranged to have piano lessons at the training centre with her sister

定语从句：where she would stay for an hour，修饰centre。

这叫定语从句的分隔现象，即：定语从句与先行词被其他成分所分隔。又如：

All are not friends that speak us fair.

The film brought the hours back to me when I was taken good care of in that far-away village.

The days are gone when we Chinese were bullied by the invaders.

The village has developed a lot where we learned farming two years ago.

After graduation she reached a point in her career where she had to decide what to do.

It was an exciting moment for these football fans this year, when for the first time in years their team won the World Cup.