How do I get out of this?

This girl (my friend) likes me and asked me to our Sadie's dance, but I don't really wanna go with her (or to this particular dance at all), but since I didn't know how to say no, or couldn't since she put all this trouble and went completely out of her way in the way she asked me, huge home-made brownie with frosting that asks me (best brownie I have ever had), so I said I think I'm going out of town after school on that Friday, but if not then I would go. Well she kinda knows I'm not going out of town so now I need help getting out of having to go.