Visiting an junkfood junkie this weekend- how do I stick to my diet?

I'm 15 and recently gained about 10 pounds in 2 months and I lost 5 pounds in the past 3 weeks. She only has junk food in her house and they eat a lot of fried stuff. I'm probably going to be there for 3-4 days- how can I make healthy choices besides eating next to nothing??