Please please help!

My little 4 year old girl got an ipad for christmas and had been playing minecraft since, and has built a really impressive world of shops, cafes, houses, restaurants, hospitals, police stations and so on.

She went to go into her world today (it was a flat creative world) and there were suddenly loads of mountains, waterfalls, animals, lava etc, etc all over all the stuff she has spent months building - obviously, she's completely distraught at losing all her world and all the things she spent so long making...

How do I get it back to normal? All her things are still there, the world still loads - -just most of the things are now halfway into a mountain, covered in water etc!

Please help!