Tell your friend to log in to the web page - outlook.com - with her Hotmail details to check that the account is still live.
If this works then it's an issue with the IMAP/POP email settings on the PC/Laptop/Smartphone.
People have been getting confused with Microsoft's definition of "Alias" within the Outlook settings in conjunction with any new Outlook addresses/aliases which may have been set up.
If you were to delete the Hotmail alias in error within the Outlook settings, then you have deleted the email address and lost all stored emails. Some say there is a chance to resurrect the account after 30 or 60 days.
Zen Unlimited Fibre 1 - 30/6