Theyre not mutually exclusive, she was definitely tripping on power, as evidenced by her refusal to give up that power when she found out about the Pah-Wraith ploy Dukat was pushing on her.
But she definitely thought what she was doing was for the betterment of Bajor. She assumed she knew what was best, and any dissenting opinions were unequivocally wrong.
Its never as easy as pure good and pure evil, especially with well written characters.