I agree with your correction but as I found the following sentence in an Italian book I just wanted to know if, in your opinion, an English mother-tongue expert could have written it.

Question

She is such a one-sided character, however, as (?) never to hesitate.
Correction ......, that she never hesitates.

Answer 1

If you mean this, you are correct:

She is such a one-sided character that she never hesitates.

You can read about the so ... that and such ... that relationship of clauses here:
http://www.grammar-quizzes.com/8-8.html