My Mother’s Hotmail account has been deleted and seemingly ceased to exist over night, how do I get it back?

Hello, it's my first time posting here. I just don't know where else to go, I've tried googling solutions, but only pull up people having their emails deleted, not their accounts. My Mother has had this Hotmail account for a VERY long time and accesses it everyday. It has all her personal information, and important documents relating to her monthly income.

Things I've tried:

1) Signing in from a different computer.

2)Tried altering the email from Hotmail to Outlook. But the account with the same name as hers on Outloook has a different owner and different phone numbers to recover the password.

3) The strange thing is, I tried registering with the same name again, but it says that her email is not available.

4) Emailing it from another account, the email bounces back and sends me a post delivery failure notification.

5) Tried sending a ticket to Microsoft as requested, they emailed a few hours letter verifying that the account never existed.

However, that isn't the case because I have email history of it being active.

6) I've tried calling the Microsoft Technical Support, and I was sent here.

7) The account was in frequent use prior to today.

I don't know what to do. If anyone has any idea what's going on, or can offer some semblance of help, I would greatly appreciate it.

Please, her email has a lot of delicate information.