What's the title of this book (10 points for the first person who answers)?

There's a girl who thinks she's been abducted by aliens and forced to work in a circus, but really it's a group of people taking the adrenaline from the young kids and teens, and using it to keep old people alive. There's twins, one of whom dies when they're forced to do their act higher in the air because it wasn't exciting enough on the ground. And the main character gets taken away to be a pet, and gets put in a clear cage where the older woman uses gloves to touch her.