Well of course she will need to notify all her email friends of her new email address and if she subscribes to any newsletters, etc she will need to resubscribe with the new address.
Websites like Facebook, Forums, her bank (if she does online banking), credit cards, medical care, credit cards, etc ... basically any site that sends her emails or where she pays bills online, she will need to go to those websites and change her profile on each one to point to the new address.
As for programs that are installed on your local PC, such as Skype, she should be able to open the programs and go to the options/settings to change her email.
Obviously this is all a lot of work but it is what you have to do any time you change your email.