If you really want to make it easy as well cheap, ask someone to teach your mother how to  use calling card in Nepal and set up a mutual time you can be reached. It is only 6 rupees per minute direct call and less if used calling card vs 9 censt per minute and many times call does not go through, very static and you will be loosing money ( I did 4 dollars). If you think the call must start from yourside  ( most people who came to USA think that call must be made from him or her , is it a status quo issue?) my suggestion does not apply.