Why Does My iPad With 5.1.1 Version iOS Can't Access Some Apps After Updating iPhone 6? Here's The Reason Why.
When you say 5.1.1 version you mean iOS version 5.1.1? This is about 5 generations older than what is available now. A lot of the apps won’t work on an older iOS like that.
She may be able to update the iOS to 6 on some of the older models, but the older it gets, the fewer apps will work on it and it stops being compatible with newer devices.