The correct sentence is: ‘Everyone except her accepts the president.’
Here’s why: In English grammar, when we use the word ‘except’ to exclude someone or something, the pronoun that follows should match the object case. In this case, ‘her’ is the object pronoun, and it’s the correct choice because it comes after a preposition (‘except’). On the other hand, ‘she’ is a subject pronoun, which is not appropriate in this context. Thus, the sentence should read, ‘Everyone except her accepts the president.’