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.
She is such a one-sided character, however, as (?) never to hesitate.
Correction ......, that she never hesitates.
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
To determine if an English mother-tongue expert could have written the sentence, we can analyze its structure and grammar.
The original sentence "She is such a one-sided character, however, as (?) never to hesitate" may sound a bit unusual in English. It uses the comparative structure "such as to" to express the intensity or extent of an action. However, this construction is not commonly used in modern English.
The corrected sentence "She is such a one-sided character, however, that she never hesitates" is grammatically correct and more natural-sounding. It uses the conjunction "that" to introduce a dependent clause, indicating a result or consequence.
In conclusion, the original sentence seems to be grammatically incorrect or outdated in modern English. It is less likely that an English mother-tongue expert would have written it in this form.