Numbers appear with country code in message app
It might be how the previous phone she had save the data on the sim card and the iPhone couldn't import it properly and misplaces the data in the import processes.

I suggest you try once again with the same phone with different sim card [or even the same sim card and see]

This will make sure that the phone doesn't have a problem.

Because to me the importing data from sim card most likely a software issues which easy to solve.