If she is backing up thru itunes on a pc there might not be enough memeory on the pc. Or maybe she needs more storage for icloud. you only have 5 GB free.
But im not an expert just my guess
As i said in my original post, it's iCloud backup, not iTunes.
She doesn't need more storage, as she has only 20 photos in Camera Roll, and in any case all major apps are switched off in Settings, Manage Storage, so there should be very little storage required.