Frozen updating iOS on iPhone 5


I have simple question, my mom is updating her iPhone 5, but she is not in the same country as me, so I am helping her over net. She had iOS 6 and going on iOS 8.1.3 - she had it already downloaded in phone, and do it over the air, but we think she forgot turn on wifi, so she prolly started update on her t-mobile 4G, in Czech where is me, we have 3G - but means fast internet data. OK her phone did all what should, made first reboot, and second reboot, but after second reboot it freezed almost at the end of line which we always see during installation. And it is not moving few hours. Where can be a problem? Slow internet from t-mobile or before iOS 6 only in the phone, or that we forgot turn on wifi in the phone?? Should we wait or if not, what to do? We did also installed latest itunes and download this iOS to computer, also we did backup to computer in itunes. So, hope she wont lose data.

Thanks a lot for all advices.