Can I undo an alias?

Hi Nina speaking here, although my username will probably  say Leana. My friend Leana was recently having some trouble accessing her outlook account and had some emails from Microsoft sent through to my Hotmail account to fix and allow access back to her own email. She's successfully fixed whatever problem she was having with her account but has accidentally changed my primary hotmail alias to her outlook address. I've since then tried to sign into my hotmail account and it's comming up with the message "The Microsoft account you've entered does not exist." I need to be able to access my account as it contains important work and study emails and basically everything I use via the net is connected to my hotmail. How do I get it back, please tell me I can!
Thank you.