for Deadly Pink by Vivian Vande Velde
Grace Pizzelli is the average one, nothing like her brilliant older sister, Emily, who works for Rasmussem, creators of the world's best virtual reality games. The games aren't real, though—or at least they weren't. Now Emily has hidden herself inside a pink and sparkly game meant for little girls. No one knows why, or how to convince her to come back out, and the technology can't keep her safe for much longer. Grace may consider herself average, but she's the only one who can save Emily. So Grace enters the game, hoping to talk her sister out of virtual suicide before time runs out. Otherwise Emily will die—for real.
Publisher description retrieved from Google Books.