She is not writing.对.
1.do叫助动词,顾名思义是帮助主要动词构成否定、疑问等.如
She does not write.(用了do或者does等,后面的动词要用原形,不能用does not writing)
Do you like it?也不能说 Do you liking it?
2.is是be的一种形式,它有两种用法,一种是作为系动词,后面跟表语.如
I am a student.
He is a teacher.
第二种是作为助动词,与主动词一起构成时态、语态等.如
He is writing a letter.
(be + 现在分词 构成现在进行时态.你不能说 He is write a letter.也不能说 He does not writing a letter.)