How can I still eat healthy?

One of my closest friends is a little bit overweight. Okay, maybe a little more than that. We do a lot of things together, like sleepovers and going to the movies. At my house, we eat the way I eat, which is always healthy things. But when we go to her house, it's always late night oreos and pizza. We went to the movies yesterday, and I got really nervous because she wanted to get this combo with a large popcorn and two icees. I know icees only have like, 80 calories (despite the main ingredient being high fructose corn syrup), but man! A large popcorn. So instead we just both got icees and she got nachos, too. How can I still eat well with her when she's eating all these things that I know I really shouldn't eat?