We had something similar happen to us when DD2 was 9 months old. We accidentally dropped her in our back garden, and she sustained a spiral fracture to her femur. I can assure you there were no twisting forces involved! Children's bones spiral fracture because they are more pliable and therefore tend to bend and buckle before they break completely. That said, one possible scenario comes to mind in your case - you mention that your nephew said she "rolled and hit her head" - if she rolled while her leg was trapped, possibly under him if he was lying on her or being rough with her, then there would be some twisting force involved.
Bookmarks