The correct option is A as if
The expression on the person's face here is in the same manner as when one has seen a ghost, the sentence requires a compound conjunction that expresses the manner in which the person has reacted. All the options here are compound conjunctions, that is, phrases that link together clauses/sentences, performing the role of a conjunction. From the given choices, 'as if' expresses an imaginary situation, or an unreal situation, used to describe a particular reaction or manner in a better way. "She has seen a ghost" is an unreal situation, hence option C is the correct answer. 'Even if' also refers to an imaginary situation but does not express the manner or behaviour, but a condition or a supposition, hence option B isn't correct. 'As well as' refers to an additional piece of information, an additional clause linked to the first one. It merely adds one clause to another, whereas here the clauses are related in terms of manner, where one of them explains the manner of her look like the one when someone sees a ghost. Hence option A is incorrect. 'In order that' is used in purpose-related sentences. It means 'for the reason that' followed by the clause that goes on to explain that reason, for example, 'Casper suddenly appeared in front of her in order that she gets frightened', where the clause 'she gets frightened' is the reason why Casper appeared so suddenly. The given sentence isn't purpose-related, hence option D is incorrect.