The correct option is C as soon as
In the sentence, the lady was struck with admiration when the violinist started playing, so the events "violinist started playing" and "struck with admiration" happen one after the other, such that there is a very little time difference between the two, as one happens immediately after the other. Hence, a compound conjunction that refers to such a situation is used (Compound conjunctions are phrases that link together clauses/sentences). 'As soon as' expresses time and it means 'immediately; at the moment' and is relevant to the sentence, as 'she' was immediately struck with admiration, from the moment the violinist started playing. Hence option B is correct. 'In order that' refers to purpose, it means 'for the reason that', where one clause explains the reason behind an action that is taken out in the other clause. The sentence here is not purpose-related, but time-related. This makes option A wrong. 'As well as' means 'in addition to', it is used to link one clause as an additional piece of information to the other clause, and the sentence does not have an addition. Hence option C is incorrect. 'As if' is used to express the manner or behaviour in which something is carried out. One of the clauses is a hypothetical situation that may or may not be true, to express the manner of an action carried out in the other clause, for example, 'She was working her shift as if it were her last'. The given sentence does not express manner, hence option D is incorrect.