As mentioned above, this is all due to your self-esteem issues. There is no such thing as objectivity in human behaviour, but I know what you mean; people would scale her higher on the attractive chart than they would you. Okay, even so, the fact that she's into you suggests that you have some sort of attractiveness to her that outweighs your acne. She was able to look past your acne and look at your qualities. These are the kinds of people you want in your life.
If she's into you that's all that should matter, its between you and her; not you, her and the rest of the world.