我猜想，或许你是拿不定这个句子中的不定式是定语还是状语吧。

其实，句中的不定式 to say such a thing 在形式上是用作定语修饰名词 cheek，cheek “无礼，厚颜无耻，恬不知耻” 是抽象名词，但这个不定式在意义上却是表示 “结果”。句意：她厚颜无耻地说出这样的话。

这是 “have + the + 抽象名词 + 不定式” 表示 “如此......以至于……；非常……结果……” 的一种句式。又如：

He had the luck to find a satisfactory job. 他非常幸运，找到称心如意的工作。

= He was so lucky that he found a satisfactory job.

= He was lucky enough to find a satisfactory job.

= He luckily found a satisfactory job.

He had the bravery to save the child from the flood. 他非常勇敢，从洪水中救出了那个孩子。

= He was so brave that he saved the child from the flood.

= He was brave enough to save the child from the flood.

= He bravely saved the child from the flood.

▲ 这种结构中的不定式还可以用 of doing 来表示，of doing 也是用作定语。如：

I had the folly to trust such a man. 我真愚蠢，竟相信这样的人。

= I had the folly of trusting such a man.