Hi

I need to put an iPhone 4S with a broken Power Button in a state that looks like it has an error (DFU, restore mode, or such) and needs to be restored. The data must be kept however.
My ex gf has my old iPhone and bought herself a new one and now she's returning it.
i go to her to set up her new and take back the old one.
i need to make her believe i reset the iPhone and the data is deleted.

but the data must be kept