Are you looking for a linguistic answer, or a political one? I'll take on the former here! The phrase "the EPA's Midwest chief[,] and an Obama appointee" is appositive to another noun, i.e. "Susan Hedman", and describes it further. Because the phrase is set off by commas, it's not essential to the sentence, but it does add information, and one element of that is to say Susan Hedman was an Obama appointee. (You may be confused by the second comma in the sentence. It's not usual to use a comma before "and" with a pair of noun phrases like that, particularly when they are short. It also miscues the end bracketing of the appositive phrase, and so I would have left it out myself. But it's a question of style, and a writer may use a comma if they feel like it.)

You can be sure that the sentence is written correctly. There are two clauses: 1. the EPA's Midwest chief, 2. and an Obama appointee. The 'and' in the second clause is a conjunction that allows us to learn more about Susan by way of the second clause. Conclusion: "She is also an Obama appointee."

Susan Hedman was an Obama appointee, but I don't think that the sentence, as it is written, allow us to draw that conclusion,

Susan was the appointee, this is because she was given the appointment (or position) by the Obama administration