Hey there! Nice to meet you!
Since your girlfriend does not have access to her verification method (recovery phone number) for a password reset, I'm afraid the only way to recover/unblock the account is through the account recovery web form: https://account.live.com/acsr
Important: If she has an active 2FA, ACSR will inform her that her recovery request will be ignored. If she only receives a message that the recovery request is either successful or indicates insufficient information, this means that 2FA is disabled.
She'll need to keep trying until she is verified by Microsoft, and she can do this up to 2 times every 24 hours.
If she didn't receive the results from the account recovery webform, please try submitting another request via Incognito/InPrivate window and using different devices and network services. Then please check her email inbox, junk, and spam folders.
If her Microsoft account recovery request was not granted, please review this link for tips on improving her chances of a successful recovery: https://support.microsoft.com/office/dc56c3e3-dff0-4ed5-8edb-60290eea6b53
Please be advised that Microsoft Support will not be able to assist with manual recovery, unblock, and escalation for this case, as stated in this article, that they are not permitted to send password resets, access, or even change any details on the account:
Thank you for your understanding.
Best regards,
Darhyl