The correct option is D She does everyone's job but her own.
We use but as an alternative to except (for), apart from and bar to introduce the only thing or person that the main part of the sentence does not include. It is often used after words such as everyone, nobody, anything, anywhere, all, no, none, any, every.
But is used as a preposition when we put a noun or pronoun after it.
Option D is correct. It means that she does everyone's job except for her own. The noun phrase 'her own', which also acts as the object of the preposition 'but', follows it.
Option A is incorrect because 'but' has been used as a conjunction to join the two sentences.
Options B is incorrect because the sentence construction is wrong.
Option D is irrelevant to the context.