Make sure your mum po is aware the smartphone may "consume data" when she is not using it I dont know how tech minded your Mum Po is but I know of plenty of new non techy smartphone users who get a little upset with how much data they consume even when not doing anything with the phone
Worth finding one where data can be switched off when not using if calls on skype are not expected if she has no general day to day need of data services
From experience not all phones are easy to switch off the data services only and keep the phone radio on
