Don't know if any anons have already stated this, but after an hour or so of examining pixel by pixel, it wasn't forensic evidence that led me to the conclusion, but glaringly obvious inconsistencies between the UI and the model of phone she's holding.
Look at the delete/backspace button on the keyboard. It's a gray background, and the icon is a black outline, with a grey interior. This button design was last seen on iOS 7.
When iOS 8 rolled out, the delete button was redesigned, having a grey background, and a solid white icon, with only the "X" in the center being cut out, to reveal the gray background. no outline, no black.
Ok, so her OS is, at the newest, iOS 7, which was released September of 2013.
Her phone has no button on top, but has a button on the right side, a design first introduced in 2014 with the iPhone 6—which shipped with iOS 8 already installed. In fact, the iPhone 6 (or newer iPhones with the power button on the right side, and no button on the top) can't even run iOS 7. The newest model of iPhone that is capable of running iOS 7 was the iPhone 5c.
So, basically:
Delete/backspace button shows use of an operating system running on a phone that cannot run that operating system. There's your evidence of fakery.