Miscellaneous topics that do not fit into specific categories.
Hello
I am sorry for your loss.
Unfortunately, you cannot try to unlock it if you are not the owner of the account. You will have to go through legal process to request access to her account.
Microsoft explains the process here: https://support.microsoft.com/en-us/accounts-billing/manage/accessing-outlook-com-onedrive-and-other-microsoft-services-when-someone-has-died
I am not sure which country you are in. If you are in the US, you need to contact the Secretary of State office and find out the contact of Microsoft's registered agent in your state. Microsoft will only respond to non-criminal subpoenas and court orders served on Microsoft's registered agent in the requesting party's state.