一个美国的课程中听到what she does is create for her students,为什么is后用了原形

感觉你这句话在create 前面少了个动词不定式符号to，应该是：
What she does is to create for her students. 这里to是不能省略的。
这里to create for her students 是不定式短语，和系动词is一起做句子的谓语。当然，还有一种分析是把不定式短语当做表语。这些都是语法界的小分歧，本质都是一样的。

关键在is前有动词do，而这个do是作为实意动词，而非助动词使用。

what she does is create for her students
句子不对，估计你听错了，应当是：what she does is to create for her students 才对。漏听了 to。

你好。在what she does 这样的句子后面如果是is + 动词原形构成的表语，这个动词原形的前面可以不加to. 又如：
Yesterday what we did was (to) visit the new park and (to) see a new film.

这个句子本应该使用is to create for her student.由于前面使用了what she does,所以后面就可以省to.再比如what you have to do is eat two oranges each time.