Question

i know what she wants. change in negative form ​

Answer 1

Here's your appropriate answer.

During transforming (changing) a sentence into its negative form, we cannot change the actual meaning of the sentence.

Thus, the answer will be :

It is not that I don't know what she wants.

(Verify/Check : See the meaning of the sentence is still now same. Even if it is converted to negative form, the meaning still remains same. So, our answer is perfectly correct)